Photo: Mauricio Alejo

You know how some people are unlucky in love? I was always unlucky in exercise. I'd get into a relationship with a workout program or guru, we'd go steady for a few intense months, and then we'd have a really ugly breakup. My elastic-waist pants would come out, the numbers on the scale would soar, and empty Ben & Jerry's pints would soon be covering every square inch of my coffee table.

It started innocently in 11th grade, with Richard Simmons. I tried so hard to sweat just the way he liked. I thought if I tried hard enough, I'd fall in love.

Instead, the romance fizzled. After a while I fell for Billy Blanks, but that fizzled, too, and for decades the promiscuous cycle continued. I'd divorce my step class, then rebound with Zumba; leave the spin studio and hook up with CrossFit.

Eventually, I had to face it: My fitness affairs had no happily ever after. In fact, the only fairy-tale-ish part was when the clock struck midnight, I burned out, and my stomach became a pumpkin again.

Finally, about a year ago, after a disastrous stint on a Pilates Reformer machine, I realized that exercise will never be my lover. Or even my friend. For me, a workout is more like an annoying coworker I have to see a few times a week. I just had to find a way to stand it. So I began to research the psychology of habit formation. And I learned I needed to do two things I'd never tried before: lower my expectations and exercise less.

In the past, coming off weeks of bad behavior, I'd always begun a new workout program highly motivated. ("What brings you here?" a trainer once asked. Well, I thought, last night while undressing, I found a pile of Oreo crumbs in my cleavage.) Stinging from guilt, I'd exhaust myself in marathon exercise sessions. I assumed I was building willpower in addition to muscle. But when I asked psychologist Roy Baumeister, PhD, coauthor of the book Willpower, I learned that self-control is like a muscle in another way: Overuse leads to exhaustion. I'd been trying to become a self-control Ironman overnight. By repeatedly pushing myself to the limit, I was draining my willpower reserves the way a shopping spree depletes a bank account.

Rather than attempt another challenging program, Baumeister advised, I should set the lowest goal I could feel good about, then try to exceed it by as much as possible. Succeeding at shorter workouts instead of failing at longer ones would bolster my confidence, and having a manageable standard would help me exercise more consistently because I wouldn't get burned out after a few weeks.

Psychologist Suzanne Segerstrom, PhD, author of Breaking Murphy's Law, reinforced that point when I called her for advice: When forming a new habit, choosing a sustainable behavior is crucial. I needed a workout I could stick with.

Unfortunately, I had no idea what that would look like.

Next: How she found "the one"