What keeps you from exercising more? You know you should. Exercise prevents heart disease, hypertension and diabetes, and is your best friend when it comes to living a healthier, happier lifestyle. But forget that. Should-a, would-a, could-a.

Let me guess your excuse: too busy! It's the No. 1 excuse in America, right up there with the dog ate my sneakers.

As your most personal trainer, I advise you to please wise up. Not having enough time to work some physical activity into your day — walk the stairs, bike to the store, do a few yoga poses before lunch — is the lamest of excuses. Make exercise a priority, and you'll find the time. You'll walk at dawn, you'll replace happy hour with Zumba classes, you'll spend fewer hours on the giant time suck known as Facebook.

Recently I read about Scott Olsen, the inventor of Rollerblades, who is so devoted to physical fitness he pulls off 150 push-ups while waiting for his gas tank to fill. Super. When you wake up and discover how terrific exercise makes you feel, how it adds joy to your life and life to your years, you'll make the time.

So what else might be holding you back from getting fit?

That's it, dig a little deeper.

Maybe it's fear.

Upward of 50 percent of people drop out of fitness programs within the first six months. Sport psychologists and other researchers who've interviewed the dropouts have uncovered the fear factor. People fear that they can't do the exercises correctly. They fear that they look stupid doing them. They fear that people are standing around judging them.

So let's look at those fears head-on and explore ways to deal with them:

FEAR OF DOING IT WRONG. This is a reasonable fear because it's painfully true that if you don't learn the correct way to hit a ball, or lift a weight, or do warrior pose, you can create injuries.

So learn! Take classes, read a book, work with a good teacher or trainer. Learning to strength-train safely isn't like learning to speak Chinese. You can master it easily if you're mindful and patient. Ditto for whatever sport or activity you want to pursue. Approach it with a beginner's mind. Ask questions; understand the basics of injury prevention. When confidence replaces fear, the ease of exercise increases mightily.

FEAR OF LOOKING STUPID. Chances are this fear began when you were a kid and grew up thinking you were klutzy and uncoordinated. Too bad someone smart and loving didn't get to you and help you discover that there are no stupid moves when it comes to being active. Every move is bringing you further down the road to better health and greater energy.

You may not be the slimmest, fastest or most graceful person in your class or on your team, but so what? As we say in yoga, keep your eyes on your own mat. Enjoy the athlete you are, doing the best you can, and keep moving. When you stop judging yourself as too fat, too slow, too stiff, fears about looking stupid in front of other people will disappear.

FEAR THAT PEOPLE ARE JUDGING YOU. This is an ego thing, so let it go. Hard truth: Everyone else is just as absorbed in himself as you are in yourself. When you start imagining that others are watching you critically, simply come back to the sound of your own breathing. Focus on your performance, your own body, your relaxation. Fitness isn't ice hockey — it's not a competitive sport. It's a personal journey. Turn your attention inward, find joy in the moment. Allow that useless fear of being judged to melt away, like that extra flesh that keeps your jeans from feeling really comfy.

If you feel that personal anxiety is behind your failure to exercise more, get some help. Talk to a qualified listener, join a support group, start a journal. Acknowledging fear is the first step toward overcoming it.

Have you overcome fear on the way to fitness? Email your story please!

ENERGY EXPRESS-O! I'M AFRAID HE'S RIGHT

"He who is not everyday conquering some fear has not learned the secret of life." — Ralph Waldo Emerson

Marilynn Preston — fitness expert, personal trainer and speaker on healthy lifestyle issues — is the creator of Energy Express, the longest-running syndicated fitness column in the country. She has a website, http://marilynnpreston.com and welcomes reader questions, which can be sent to MyEnergyExpress@aol.com.