We all know we need to get off our couches and on to our feet for a good sweat, but despite the fact that working out makes us look great, feel great and live longer, 50 percent of people who start an exercise program drop out within six months. "Exercise is hard work and people want quick fixes," says James Gavin, Ph.D., a sports psychologist and professor at Concordia University in Montreal, Quebec. "But a quick-fix attitude doesn't lead to long-term commitment." Here's why—and what you can do about it:

1. You narrowly define exercise. Most of us have a specific view of what constitutes exercise (i.e. "I must be at a gym wearing my gym shorts and sweating profusely"). Such a limited view of what constitutes "exercise" could be severly limiting your workout opportunities. "Think about the parameters you're applying to your workout regimen and then throw them away," says Gavin, who recommends finding less rigid ways to get in some regular fitness. "As long as working out is separate from your life, you'll always struggle to force it in."

2. You have a narrow view of yourself. It's all too easy to latch on to one activity you like. The next thing you know, you're a Runner, or a Yoga Person, or a Spinner. But categorizing yourself this way can keep you from trying new things—and you end up bored, Gavin says. Instead, look at fitness as an opportunity to discover new things about yourself through challenge. Instead of recommitting to your old regimen, just try something that sounds fun.

3. Your goals are strictly physical. The top reasons men and women work out are for weight control and muscle tone, respectively. But people who really stick to it know that looking good is just part of the story. When a group of runners were asked "Why do you run?" 80 percent of the people who stuck to it for over a year gave psychological reasons (in contrast to the 80 percent of people new to running who cited physical benefits). "If people could see fitness as a way to support, reinforce or balance their life needs, and choose activities according to those needs, they wouldn't need to recommit," says Gavin.