When the leaders of the world dispense advice to the next generation, they tend to emphasize the same message: Help others. That was a key theme in almost two-thirds of the talks in a study of graduation speeches at U.S. universities.

Graduates are promised by those who have “made it” that being generous — readily sharing their time, energy, and expertise — will lead to a successful career and a meaningful, happy life. It can, but it doesn’t always. The road to exhaustion is often paved with good intentions.

Four years ago one of us, Adam, published a book called Give and Take. It was about how generous “givers” succeed in ways that lift others up instead of cutting them down. It turned out that givers add more value to organizations than selfish “takers” or quid pro quo “matchers” do.

Givers do the lion’s share of connecting, as in “Hey, Steve, you should meet my other friend Steve because you both love computers and playing pranks.” (These two guys went on to found a company called Apple.) They stick their necks out to sponsor promising people and ideas: “I know this show is about nothing, and the characters aren’t likable, but it made me laugh.” (Seinfeld got another shot at NBC.) Givers share their knowledge freely: “You know your adhesive that won’t stick? Why don’t you use it to create a bookmark?” (Post-it notes were born.) And they volunteer to do the heavy lifting: “Sure, I’ll take a crack at rewriting this script.” (Frozen got the green light.)

Although givers are the most valuable people in organizations, they’re also at the greatest risk for burnout. When they don’t protect themselves, their investments in others can cause them to feel overloaded and fatigued, fall behind on their work goals, and face more stress and conflict at home.

Adam’s book made the case that givers can rise to the top, but it only scratched the surface on the question of how. We’ve spent the past four years studying what givers can do to sustain their energy — and their effectiveness. That’s what we’ll discuss here, after we look at how the well-meaning but overly altruistic get in their own way.

When Good Intentions Go Wrong

Givers at the top are often called servant leaders. They selflessly put the needs of others first, and that helps drive their firms’ success: A study of technology companies revealed that when CFOs agreed with statements like “The CEO seems to care more about the organization’s success than his or her own,” their firms had significantly higher returns on assets in the following quarter — relative both to other firms and to their own past performance.

You want the top boss to put the organization first. But do you also want everyone else to be selfless?

To find out, we’ve been studying people in a wide range of jobs. Some of our favorite recent data points come from more than 400 second-year teachers (from pre-K through high school throughout the United States). At the start of the year we asked them a series of questions about their approach to helping; their answers allowed us to predict how well their students would do on end-of-year academic achievement tests.

Here’s a sample question:

Teaching is a helping profession, so we knew we’d find plenty of highly motivated givers. We wanted to see how much they would sacrifice themselves. We gave them 11 scenarios — some with requests from students, others with requests from fellow teachers or administrators. The more times teachers chose answers like (a), the worse their students performed.

Option (a) is what we call a selfless response — helping without boundaries. Compared with their self-protective peers, selfless teachers saw significantly lower student achievement scores on standardized assessments at the end of the year. This effect was especially pronounced for teachers whose students had performed poorly the previous year. Selfless educators exhausted themselves trying to help everyone with every request. They were willing to work nights and weekends to assist students with problems, colleagues with lesson plans, and principals with administrative duties. Despite their best intentions, these teachers were inadvertently hurting the very students they wanted to help.

This kind of dilemma isn’t unique to teaching. As we wrote in an HBR article with Rob Cross last year, collaborative overload is pervasive in workplaces around the world, and selfless givers are its biggest victims. Employees who consistently demonstrate the motivation and ability to lend a hand get “rewarded” with the bulk of requests and often find themselves drowning in meetings and emails. The result is that they are at risk of burnout or attrition, their colleagues are frustrated by a lack of access to the help they need, and other employees who could be pitching in are instead sitting idle and disengaged.

Meanwhile, our research shows that across industries the people who make the most sustainable contributions to organizations — those who offer the most direct support, take the most initiative, and make the best suggestions — protect their time so that they can work on their own goals too.

People often make the mistake of confusing generosity with selflessness. As the writer Caroline McGraw observes, “We’ve been conditioned to believe that being kind means being available 24/7.” Being an effective giver isn’t about dropping everything every time for every person. It’s about making sure that the benefits of helping others outweigh the costs to you. Finding ways to give without depleting your time and energy — as in choice (b) in the sample question — is generous but not selfless. The teachers who took that approach didn’t see their performance suffer the way their peers who made a habit of going way above and beyond did.

Effective givers recognize that every no frees you up to say yes when it matters most. After all, it’s hard to support others when you’re so overloaded that you’ve hit a wall. As comedian George Carlin put it, “They tell you to adjust your oxygen mask before helping your child with his. I did not need to be told that! …This will be a good time for him to learn self-reliance.”

We’ve discovered that productive giving comes in three flavors: being thoughtful about how you help, when you help, and whom you help.

How to Help: Jack-of-All-Trades, Stuck with a Ton

Ad hoc requests for help are among the biggest drains on people’s energy and time. When we studied managers, engineers, and salespeople at a Fortune 500 technology company, more than 60% said they would like to spend significantly less time in “responding” mode. And other research suggests that 75% to 90% of all the helping in organizations is reactive: Someone makes a request, and we respond. Great to meet you, burnout.

In a new study, researchers surveyed managerial and professional employees every day for three workweeks. The more times people responded to help requests from coworkers on a particular day, the more their energy was depleted — and the more trouble they had focusing their attention and persisting with difficult tasks. This effect lasted until the next morning, and it was especially strong for givers who’d made sacrifices to go the extra mile for their colleagues.

Reactive helping is exhausting, but proactive giving can be energizing. We’ve seen this with Adam Rifkin, who has been recognized as Fortune’s best networker for having an unusually high number of ties to powerful people. Rifkin is a computer programmer who founded a series of technology startups and did well enough to retire in his thirties. As word spread of his generosity and success as an entrepreneur, he was bombarded with requests for business plan advice. (“Dear Mr. Rifkin: I know we’ve never met, but I was wondering if you would read my 274-page business plan and then meet with me for coffee to discuss….”)

Rifkin didn’t have time to meet with everyone who asked, and he didn’t particularly enjoy dispensing business plan advice. So he decided to start giving on his own terms. He had a knack for matchmaking — connecting strangers was his favorite way to help others. One morning he set a goal: Every day he would make three introductions between people who could benefit from knowing each other. He did that for the next decade, making more than 10,000 introductions and opening doors that allowed hundreds of people to find jobs and dozens to launch companies. He also accidentally arranged a couple of marriages: He told people, “Hey, I think you two would hit it off professionally,” and then — whoops — they fell in love.

Bursts of lava from Mount Etna, one of the world’s most active volcanoes, where violent eruptions regularly send hot lava and ash high into the sky, affecting the climate for miles. (SOURCE: Getty Images)

Reactive helping is exhausting, but proactive giving can be energizing.

As Rifkin started making introductions, he noticed that the business plan requests dropped off. Before, he’d had a reputation as a nice guy, someone who would help anyone with anything. He was stuck responding to the full suite of requests that flooded his inbox. Now he was known as a great connector. People started taking their miscellaneous requests elsewhere, because why would you go to Fortune’s top networker for business plan advice when the best resource he can offer you is an introduction?

We all can be more thoughtful about how we help. Building on a nationally representative poll of Americans, we’ve found six profiles of giving:

  • Experts share knowledge.
  • Coaches teach skills.
  • Mentors give advice and guidance.
  • Connectors make introductions.
  • Extra-milers show up early, stay late, and volunteer for extra work.
  • Helpers provide hands-on task support and emotional support.

Don’t try to be everything to everyone. Cast your eyes over this list and think about what makes sense for you. Identify two or three ways of offering unique value to others — things you do well and enjoy.

As giving aligns with your interests and skills, it becomes less stressful for you and more valuable to others. Rather than feeling pressured to help, you’re choosing to help, which is good for your motivation, your creativity, and your well-being. Instead of being known as a jack-of-all-trades, you’re seen as a master of a few. That frees you up to focus on helping where you have the most impact — which replenishes your energy by reminding you how much your contributions matter. It gives you license to turn down requests that aren’t in your wheelhouse, because you have a track record of helping. And it allows you to make choices about when to step up.

When to Help: It’s About Time

Ryan Daly served as an army lieutenant in Iraq, surviving an ambush and losing four men in 15 months. Upon leaving the military, he went to business school and made a personal commitment to help others with their career transitions. Soon he was fielding 40 calls a month from veterans. As word spread of his generosity, the requests for advice ballooned. By the time Daly started his full-time job in advertising at Google, he was averaging nearly a hundred of those conversations a month.

He thought about sending out an FAQ document but decided that wouldn’t work. “It’s very important that I get back to everyone in a timely manner,” Daly told us. “But I want to give people something tailored to them.” He didn’t know how he could do both.

We suggested that Daly set up a weekly Google hangout. When people reached out, he would send them a link to sign up for it. That way, he could still interact with them directly, but he could also answer common questions in fewer conversations. He was able to help more people and feel less depleted.

As Daly had discovered, giving becomes a grind when it takes over your time. For some people — like those at the technology company we studied — a high volume of low-value requests eats into time that could be used for greater productivity or impact. For others — like the teachers mentioned earlier — going all-in on many individual help requests leads to working long nights and weekends instead of resting or pursuing personal enrichment or development. Either way, protecting your calendar is essential to sustaining generosity.

That doesn’t necessarily mean spending less time helping; it can be more about pacing yourself and allocating your time wisely. In one of our favorite experiments, psychologists asked people to perform five random acts of kindness every week for six weeks. Participants were randomly assigned to either “sprinkling” or “chunking” their acts of kindness. Sprinkling meant spreading them out by doing one a day. Chunking meant picking one day — let’s say Thursday — for all five helpful acts.

Half the participants experienced a boost in happiness and energy that lasted for the entire study. For the other half, the giving did nothing whatsoever to improve their moods. When we ask executives to guess which group got the energy spike, more than 80% vote for sprinkling. They assume that a little giving every day is a reliable way to lift your spirits. But they’re wrong. Only the chunking group got happier.

A dark canopy of ash blocks sunlight from new flowers trying to grow after a volcanic eruption in Iceland. (SOURCE: Getty Images)

Takers treat help as an open invitation. That’s how collaborative overload creeps in: What you thought was a one-off request turns into an ongoing commitment.

One act of helping a day does nothing for your mood because it’s a drop in the bucket. A distracting blip. But if you help five people every Thursday, you feel you’ve made a difference each week. And you have more flexibility to make progress in your own work the rest of the time.

Of course, it isn’t practical to organize every week or every act of generosity like this. But we can all do better at timing our giving to manage our energy. In one study of salespeople, helping others meant lower performance for people with poor time management skills but higher performance for those with excellent time management skills.

One effective tactic is batching common requests, as Daly did with his Google hangouts. Along with being more efficient for him, this approach was more beneficial for the veterans: Many of them felt alone in their transition to civilian work, and the hangouts made them part of a community.

Another strategy is to create a personal library of useful responses and resources. How many times have you written different versions of the same email from scratch? Certain types of questions are bound to come up more often than others. Sending someone an FAQ may feel too impersonal, but that doesn’t mean you need to completely personalize every response. When you take the time to explain something clearly or to put together a list of useful resources on a certain topic, why should only one person benefit? Copying the most relevant sections to a document saves time and expands the return on your initial investment.

There are other ways to streamline the giving process. Professors schedule office hours to make themselves available to students and set aside separate windows for work on their own research. This may not be a great idea with your boss or your direct reports, but you can use office hours to keep your work time from being overrun by random meetings. We both use online scheduling tools to manage requests for meetings and calls outside our core responsibilities. This allows us to draw boundaries around our availability, instead of declaring open season on our calendars. And it saves back-and-forth e-mailing to find a time that works—something people reaching out usually appreciate just as much as we do.

Of course, no matter how efficiently you manage the giving pipeline, you may still get more demands than you can meet. How can you decide who really needs and deserves your time?

Whom to Help: Hint – Not Everyone

Callie Schweitzer rose rapidly through the ranks of digital media. Just a few years out of college she began running marketing and communications at Vox Media and soon was leading audience strategy across Time Inc. She quickly faced a barrage of requests, from students seeking career advice or wanting to profile her for class papers, to journalists looking for insights about communications. The week she was transitioning to a new job, a student on a class deadline got in touch with her, wanting to talk right away. Schweitzer explained that she was too swamped for a call on short notice but would be happy to answer a specific question by email. The student followed up with six in-depth questions, asking for extensive explanations. Essentially, he was requesting that Schweitzer write the paper — on the future of journalism, no less — for him.

The bad news is that givers are vulnerable to takers. They tend to trust too readily and see the best in everyone. But that can actually make them better lie detectors, research shows. Because they trust others, they are lied to more often. Givers get to see the full spectrum of human behavior. If they pay close attention, they can learn to recognize the clues that reveal selfishness: Acting entitled to people’s help. Claiming credit for success while blaming others for failure. Kissing up and kicking down. Being nice to your face and then stabbing you in the back — or being nice only when seeking a favor. Overpromising and underdelivering. As David Aikman at the World Economic Forum puts it, “There are talker-takers and giver-doers.”

Spend enough time with someone, and these patterns tend to reveal themselves. But as we’ve already seen, time is not something givers can spare. If it takes weeks or months to realize someone is taking advantage of your generosity, you’ve already paid the price — and so have all the other people who really needed your help.

To prevent generosity burnout, you have to hone your skill at prioritizing requests and screening for sincerity. The most successful givers act like triage nurses in an emergency room: When someone comes along asking for help, they don’t jump straight into a treatment plan. Instead they gather information to determine how serious and urgent the need is, figure out who the best person to help might be, and assess whether any small remedies would be useful in the meantime. Only then do they decide how — or even whether — to help. As Caroline McGraw reminds us, “You don’t owe anyone an interaction.”

What are some other early clues that you might be dealing with a taker? Consider how the request for help is made. Givers recognize that asking for help is an imposition on your time, and they go out of their way to make it as easy as possible for you to respond. They ask for five-minute favors and offer to work around your schedule. Takers, on the other hand, contact you out of the blue and ask if you can “jump on a call today,” follow up multiple times if you don’t respond right away, and insist on meeting on their terms even though they’re the ones imposing on you.

Another sign is that when you give an inch, they try to take a mile. Givers respond to help with gratitude and a willingness to pay it forward. If they follow up, they do so cautiously and without expectations. Takers treat help as an open invitation to get more of the same. That’s how collaborative overload creeps in: What you thought was a one-off request to share some information slowly turns into an ongoing commitment to someone else’s project.

When you’re dealing with people who have a history of selfishness, don’t reinforce their behavior by being too generous. Approach them the way “matchers” would: Ask them to reciprocate or help others. And if you have a real relationship with the other party, it may be time for a difficult conversation.

Early in her career, Schweitzer felt compelled to say yes to every request. By the time the student sent his six questions, she had learned to set limits. She answered one of the questions. He never responded.

Mind the Gender Gap

People often ask us if there are gender differences when it comes to generosity burnout. When we analyzed the data, we were saddened to learn that, as you might assume, men are more likely to be takers and women are more likely to be selfless givers. It happens in workplaces around the world: Women are expected to do more of the helping, but they get less of the credit for it.

In her studies of gender differences in the workplace, Simmons researcher Joyce Fletcher observed that dynamic in action. At one technology company, a major product launch was on the verge of falling apart until a group of female design engineers saved it. They took the initiative to fix shoddy products before they were shipped. They translated technical jargon so that coworkers could understand it, taught less experienced colleagues how to address computer problems, and jumped in when their peers refused to help. They resolved conflicts between teammates, listened to frustrations, and offered advice and encouragement.

When these women swooped in to help their team, they should have been rewarded. But they weren’t. No one really noticed. When a female engineer showed a faulty product to the male quality control manager, he shrugged, so she took it upon herself to come in on Saturday to fix it. “The manager did not thank her,” Fletcher writes, “or give any verbal or nonverbal affirmation.” When the men did acknowledge the women’s help, they often dismissed it, because it appeared to threaten their own feelings of competence. In four years of shadowing and interviewing the team, Fletcher saw this happen over and over. For the female engineers, helping was a disappearing act.

Women shoulder responsibility for the giving acts that are most valuable but least visible, like mentoring behind the scenes. They get stuck with the office housework — planning meetings, taking notes. And they don’t get that time back to use for their own work, professional development, or opportunities to volunteer for higher-visibility initiatives.

If we want to stop generosity burnout, we need to shift the balance. For women, that means setting boundaries instead of being selfless. For the men who work with them, it means stepping up to do more of the helping and mentoring. For organizations, it means assigning and evaluating work on the basis of people’s contributions, not their gender. And for all of us, it means that it’s high time to stop reserving the generosity glory for men and dumping the grunt giving on women.

. . .

Although giving makes our jobs and our lives more meaningful, it doesn’t always make us more energized. On average, helping others makes people only modestly happier — and in some studies, takers actually report more pleasure in life than givers. It’s not hard to figure out why. When people are selfless to the point of burnout, they undermine their own ability to give and the satisfaction that comes from it.

Generosity means caring about others, but not at the expense of caring for yourself. By protecting yourself from exhaustion, you may feel less altruistic. Yet you will actually end up giving more.