You could always count on Kathy Church. When friends called to vent, she would pick up the phone. When there was a crisis at work, she'd dig in. When family members got together, she'd show up no matter how much she didn't want to.

Church was always game and always nice. But as she veered into chronic people-pleasing, it ate away at the good will she was trying so hard to cultivate.

Unwilling to say no to any request, Church grew stressed, unable to sleep, and resentful of the people who were taking her time and of herself for letting it be taken. Overworked, she quit her job to start her own company, but even then found herself taking on projects she didn't want because she was so worried about offending someone or being disliked.

"It was a self-esteem issue all the way around," said Church, now a recovering niceaholic, who owns a virtual administrative consulting company in Phoenix. "I didn't regard myself as important as the people I (considered) important."

Though being nice is overwhelmingly a positive trait that research has shown to be beneficial to individuals and society, a dark side can underlie its cheery surface.

People eager for approval can overextend themselves to exhaustion, their compulsive "yes"-ing driven by any number of fears: of being tossed out of the group, of confrontation, of missing out on an opportunity that may not come again, of being perceived as lazy or selfish or uncaring, said Susan Newman, a social psychologist and author of "The Book of No: 250 Ways to Say It — and Mean It and Stop People Pleasing Forever" (McGraw-Hill).

"We live under this misconception that saying yes, being available, always at the ready for other people, makes us a better person, but in fact it does quite the opposite," Newman said. "You get stressed and anxious; you're viewed as a patsy."

Niceness, of course, isn't always driven by insecurity. But even when it comes from a natural inclination to be agreeable, or years of being peacemaker, without boundaries it can backfire.

Excessive generosity can actually be repellent to those it's meant to impress. In a study published in 2010 in the Journal of Personality and Social Psychology, researchers from Washington State University had students play a game that gave individual rewards for certain actions and group rewards for others, to judge reactions to those who played particularly selfishly or particularly generously. Students condemned both extremes, saying, of the generous ones, that they made everyone else look bad.

In a 2011 study in the same journal, University of Notre Dame researchers found that men who were agreeable (the academic term for nice, warm, cooperative) earned 18 percent less than their disagreeable counterparts, and agreeable women earned 5 percent less than disagreeable female employees, perhaps because nice people are less aggressive or not so adept at negotiating. (The gender gap suggests aggressiveness is not so highly valued in women.)

The trusting, optimistic natures of nice people can make them vulnerable to manipulation by their more self-serving peers, said Ronald Riggio, a social psychologist and self-described "terminally nice guy." He recalls being swindled during salary negotiations for an academic position because he trusted his new employer to keep his best interests in mind.

"Nice people have to develop strategies to stand up for themselves," said Riggio, Henry R. Kravis professor of leadership and organizational psychology at Claremont McKenna College in Claremont, Calif."It's about being assertive but not losing your niceness in the process."

Nice people must be particularly on guard in a permissive culture that decreasingly breeds conscientious, rule-following citizens who care about how they behave or how it affects other people, said George Simon, a clinical psychologist and author, most recently, of "Character Disturbance: The Phenomenon of Our Age" (Parkhurst Brothers).

A major mistake is to assume that everyone has the same capacity for kindness and that people behave badly because of some childhood trauma, Simon said. Research has shown that some people are just wired differently; couple that with what Simon sees as a reduction of civilizing influences in our culture, and there's a "dwindling minority" of noble people left to serve as the backbone of society, he said.

"People get themselves into trouble when they give people the benefit of the doubt and they discover others don't have the same capacity for empathy," Simon said.

Knowing whom to trust can be insidious when people who appear quite charming and civil aren't so nice at all, covertly getting what they want by hitting nice people where it hurts most: guilt and shame.

Still, it's far better to be nice than not.

People who rate high in agreeableness tend to convert conflict situations into cooperative ones, which may lead them to compromise their own interests, but for people who prioritize harmony that's not always a bad thing, said Renee Tobin, a psychology professor at Illinois State University who has conducted several studies on agreeableness.

Agreeableness itself is not the problem, Tobin said, because people who are motivated to get along with other people tend to do well in life. Where trouble can arise is if niceness is driven by insecurity or if people suppress their negative emotions, which can eventually manifest itself as ill health, she said.

Life coach Vickie Champion has witnessed intense fallout among clients who misinterpreted niceness as a subversion of their needs. Constantly trying to do things for others, her clients see their family lives suffer because they're too busy to pay attention to their spouses, or their incomes stay low because they do everyone else's work and never ask for a raise.

Most don't know what their own dreams are because they're so focused on helping other people realize theirs. It gets worse with age, Champion said, as these niceaholics collect more friends to please along the way.

Underlying such compulsive niceness is the belief that otherwise the person won't be loved, said Champion, who on her website (vickiechampion.com) lists 52 traits of a people-pleaser. She advises her clients to practice affirmations, such as: "Above all else, I want to be happy."

Church, who was a client of Champion's, said it was painful to free herself from her cycle of niceness. But as her boundaries grew, so did her personal and professional success.