Back to Pretty Woman, which is really a paradigm of the wake-up call that Segal says can change negative thinking: "The Roberts character gets into a relationship with Gere that's different from one with an ordinary wealthy john. His interest in her is as more than just a hooker, and she feeds off that to explore herself." For people who don't live in Hollywood movies, a wake-up call could be reading a book that inspires you, or having an experience that shakes you out of your usual pattern. I've been thinking about Austen and Brontë heroines like Fanny Price or Jane Eyre, who come from small, mean, meager lives but blossom when exposed to the world beyond. I've heard the adult children of alcoholics talk about escaping strife at home by finding refuge with neighbors or at school, where they're encouraged by messages of possibilities. The next step is identifying the barriers in your way, Segal says: "It could be a spouse who tells you you're no good, or a boss who says you don't deserve a raise. Maybe you're someone who has grown up taking care of others but not yourself."

There is good—no, great—news about changing a pattern like negative thinking, according to neuroscientist Michael M. Merzenich, PhD, at the University of California, San Francisco, who has demonstrated how the brain remakes itself all the time. Taking recordings from the nerve cells of a monkey's brain, Merzenich and his colleagues showed how a particular area of the brain became inactive when the animal was unable to use one of its fingers. But within a few months, the neurons no longer receiving signals for that finger were appropriated for use by an adjacent part of the hand.

"The brain is not like a computer that has fixed wiring and connections," says Merzenich. "Every aspect of you is created by the brain revising itself in response to your interactions in the world—and I mean everything. How you define yourself—the person you are—is a product of plastic changes in your brain. That includes things that relate to your attitude and your emotional construct. What you are is a result of how your brain has tried to create a model of the world, and the brain is plastic until you die."

Transforming negative thinking doesn't occur instantly. "People can't just change their attitude on a dime," says Merzenich. "You're going against all that weight of experience. Thousands of historic moments have led to that bad attitude—every time you've thought about yourself in a defeatist or inferior position. That's deeply embedded, and it takes a substantial effort over a substantial time to drive the brain in a new direction." But you (and I, and anyone) can make profound, fundamental changes in how the brain operates. It's not that different from doing Pilates or taking a spinning class to change your physical self. In fact, Merzenich cofounded a company called Posit Science that produces technical "brain games" as training exercises for that highly plastic part of us. We know that we can enhance memory; now, remarkably, it seems that we can improve outlook.

For me, believing the good stuff starts with awareness. The ruminator residing inside me is not easily silenced. (Is this article good? And does it make me look fat?) But I'm at least recognizing and acknowledging when she makes an unwelcome appearance. I tell her that she's looking good, that her brownies are to die for, that she should just chill.

I may even reconsider short skirts.