A clinical psychologist, Pratch has evaluated hundreds of candidates for CEO and other top management positions at Fortune 500 companies to predict who will succeed in these leadership roles—and who will not. Her new book, Looks Good On Paper, distills down the one trait she thinks is essential for successful leaders to have.

Great leaders are great active copers, Pratch explained to me earlier this week over coffee. By active coping, Pratch means the ability to adapt creatively and effectively to challenges and change. An active coper quickly recovers from setbacks, opens up to the people around her and is aware of her own motivations, strengths and shortcomings. In the constantly changing world that we will in, it is critical that leaders posses this trait, says Pratch.

By evaluating potential job candidates based on this one trait, Pratch tells me she has successful predicted the outcome of the leader’s tenure 98% of the time over a ten-year period.

One of the key signs that tips Pratch off to a bad active coper is narcissism. Self-involved executives feel a need to view themselves as special, she explains, and in turn, they develop a diluted version of themselves and their organizations. Good active copers are self-aware and open to other opinions.

Pratch added that it is particularly important for women leaders to be skilled active copers. Leadership requires a certain level of self-confidence and aggressiveness, yet women are faced with a “heads-you-win tails-I-lose situation” when it comes to these traits. If they display too little they are deemed ineffective and if they display too much they can be viewed as full of themselves. To transcend these gender stereotypes, women must be stronger active copers and find a leadership that resonates with their entire team.

“Women are more limited in the range of behaviors that they can choose to be effective because they are penalized for behaving in traditionally masculine ways,” says Pratch. “Active coping is about having a choice over your behaviors and choosing the one that is going to be effective in that situation.”

So are there any Fortune 500 CEOs that are particularly skilled active copers? When I asked Pratch, she cited PepsiCo (PEP) CEO Indra Nooyi. The chief executive recently discussed her inability to achieve work-life balance and said she was “impressed” by her remarks.

“The first step to active coping is accurately perceiving reality,” says Pratch. “She seemed very open that there was a conflict and that women have to make a choice everyday. That’s a sign of active coping.”

Sign up for Caroline Fairchild’s daily newsletter on the world’s most powerful women at GetBroadsheet.com