Graduate and research assistantships. Conference presentation slots. Internships. Publications. Tenure-track jobs. There's a limited supply of all these things, which leads to intense competition among psychology graduate students. And that means students often try to make themselves look good by taking on more than they can handle — even though doing so can backfire.

"You want to boost your CV by taking every opportunity that comes your way," says Jesse D. Matthews, PsyD, a psychotherapist at the Center for Psychological Services in Ardmore and Paoli, Pa. "That breeds the feeling that you can't say no."

As a result, psychology grad students often find themselves juggling must-do tasks, such as classes, jobs and internship applications, with should-do tasks, such as serving on committees, attending conferences and advocating for psychology. All that's before they add family obligations, exercise, sleep and just plain fun to the mix.

While graduate students often feel they can't say no, saying yes to too much can mean spreading yourself too thin and jeopardizing your reputation, relationships and even health, warn Matthews and others. That's why learning when — and how — to say no is just as valuable as all the other skills you're learning in your graduate program.

"As graduate students, we're used to achieving a lot," says Matthews. "Sometimes we project this fantasy that we're Superman or Superwoman and that we can handle everything, but we're really human and we can't."

Saying yes when you should say no

It's not surprising that people say yes to requests when they probably shouldn't, says social psychologist Susan Newman, PhD, author of the 2005 book "The Book of NO: 250 Ways to Say It — and Mean It — And Stop People-Pleasing Forever."

Most people have a hard time turning down requests, says Newman.

"As young children and teens, we have had ‘no' drummed out of us," she says. "We're taught to do what our parents say and what authority figures tell us."

Plus, she says, people often believe that saying yes will make others like them more or help them avoid appearing selfish, uncaring or lazy. Others may not like even the mild confrontation involved in saying no to something. For others, says Newman, the habit of saying yes has become almost an addiction. "They simply can't say no to people and just pile more and more responsibility on themselves," she says.

Students can be especially susceptible to saying yes too often given the power dynamics in grad school, says Newman, explaining that many students believe they must say yes to any requests from their advisors, professors and supervisors.

Women and racial and ethnic-minority students may have an even harder time turning down requests, says Chapel Hill, N.C., clinical psychologist and academic coach Mary McKinney, PhD, who publishes Successful Academic News.

"Saying no is more challenging for women because of societal pressures to be likeable," says McKinney. "Men are still seen as likeable if they're assertive, while women are more likely to be seen as likeable if they're compliant."

Minority students face a double-whammy, says McKinney. "They not only want to please and say yes to offers, but they often also feel an obligation to try to help other minorities by being a representative on committees to make sure a minority voice is heard, for example," she says. "They may feel a commitment to helping others in ways that can sometimes impede their own careers."

But taking on more than you can handle can have dire consequences, Newman warns.

"Something's got to give," she says. "You're not going to be able to do your best work if you're so scattered because you've agreed to everything." You're also likely to get sick if you're up half the night every night, she says.

Plus, by not learning how to say no now, says McKinney, you're harming your future career, whether you plan to be an academic or not.

"Graduate students may think, ‘I'm saying yes now, but as soon as I get my PhD, I can start saying no,'" she says. "But that power dynamic of not feeling they can say no to professors continues when they are postdocs or junior faculty."

In fact, says McKinney, she's been seeing increasing numbers of tenured faculty in her practice who are now busier and unhappier than ever before. "It always seems to come back to not learning early on how to set priorities and say no," she says.

Tuning up your turn-down skills

What should you do if you're on what Newman calls "a yes treadmill"? Newman and others suggest a multi-step process for how to evaluate offers and turn down the ones whose drawbacks outweigh their benefits — without alienating the person making the request:

Consider the potential upsides

When someone asks you to do something, whether it's a professor, supervisor, family member or friend, think about how the request might further your goals, says Christine Jehu, a fourth-year doctoral student in the University of Memphis's counseling psychology program. Each semester — or sometimes as often as every month — Jehu sets her priorities, then evaluates how any request she gets fits in with those priorities. "I figure out that my focus this semester will be more clinical hours or outreach or getting a publication," she says. "If something's not in that focus, I say no."

To make such assessments easier, Jehu knows exactly what she has on her plate at any given time. She schedules "every minute of my day" and color-codes a Google calendar according to classes, APAGS work, time with her fiancée Stephanie, even sleeping and exercise.

Students should keep an open mind, Jehu adds. "Think about areas where you need to grow, and seek out and say yes to things that are going to help you [do that]," she says.

Of course, sometimes an opportunity arises that you can't — or don't want to — say no to, says McKinney. "In that case, you can look over your other commitments and see if there are any you can get out of," she says. "Or you can say, ‘OK, I really want to take this opportunity to work with a wonderful professor, but it's going to take me six months longer to finish my dissertation."

Understand what's in it for them

The people asking you to do something are usually looking out for your best interests, but that's not guaranteed, says Samuel R. Sommers, PhD, an associate professor of psychology at Tufts University. Sometimes people will ask you to do something just because they know you'll say yes, he says. "You want to be a good citizen and contribute to your department, university or discipline, but sometimes by saying yes, you just wind up getting asked more and more," he says. "There's a fine line between being a conscientious citizen and being a pushover who's taking too much of a burden on for other people." Reviewing a manuscript for a journal is a nice line on your CV, he points out, but doing multiple reviews for the same journal offers diminishing returns.

Other requesters may have more specific motivations. Women and minorities, for instance, can be in hot demand for committees, panels and other groups seeking to add diversity, says Megan Smith, a fifth-year doctoral student in Purdue University's department of psychological sciences. "Committee work, reviewing grants, APAGS work — you could get so bogged down with these kinds of things," says Smith, who spoke along with Matthews and Jehu at an APAGS-sponsored session on setting goals and saying no at APA's 2013 Convention. "My advisor has talked to me about doing the right amount of that kind of work, but not more." When Smith feels she has simply become the "go-to person," she bows out.

Make an informed decision

Build strong relationships with your advisor and others in leadership positions so that you can have honest conversations about requests they're making of you, says Sommers. Don't stop there, however. "Being able to get a second opinion is never a bad thing," he says. If you're asked to be a teaching assistant, for example, ask current and former students what the position entails, what the professor is like to work with and so on.

Keep it simple

Don't feel compelled to offer complicated excuses for why you're saying no, says Matthews. Be honest but brief. Thank the person for the offer, say you're focused on your dissertation or whatever your current priority is and move on, he says. "If you give a long, drawn-out explanation and start apologizing, the person knows he or she can probably make you say yes with a little bit of convincing," he says. Be ready to repeat your no. If you know another student who would welcome the opportunity, share that's person's name.

Don't keep the other person hanging

Don't dither, says Sommers. While it's fine to ask for a few days to think a request over, don't take too long or ignore a request. "I can deal with yeses and I deal with nos," says Sommers. "It's the people who don't respond at all that drive me crazy."

And don't fret about how the person will react to your rejection. "The fallout's never as bad as you think it's going to be," says Newman. "As soon as you say, ‘I'd love to help you, but I can't,' the person isn't thinking about you anymore; they're thinking, ‘Who can I get to do this?'"

Rebecca A. Clay is a writer in Washington, D.C.