I recently heard a popular media doctor talking on the radio about making dietary and exercise changes to promote optimal health. He gave some sound advice.

“Write down your goals. Think about why you want to lose weight and get more fit.”

So far, so good. But then he added a suggestion which flies in the face of what we psychologists know about behavior change: “Thinking about what you want to avoid is the best way to motivate yourself.” He went on to explain that a family history of diabetes keeps him on the straight and narrow. In other words, he’s motivated by fear.

Maybe this approach works for him ( though given his success, I suspect he’s more disciplined naturally than most of us anyway, so he probably doesn’t need much of a motivational boost). But it’s not the most effective way for most people to stick with a diet or exercise plan.

If scare tactics worked, wouldn’t those gruesome, anti-smoking PSAs impel more smokers to quit? Knowing something isn’t good for us—potentially fatal, even—usually isn’t enough to make us stop.

Thinking about what we want to achieve is much more motivating than envisioning the dire consequences of unhealthy habits. So if you want to get in shape, don’t imagine yourself in ten years, three sizes larger and insulin-dependent. Instead, picture yourself six months from now, crossing the finish line of your first 5K.

If you point yourself in the direction of where you want to go, you’ll get there faster than if you run the other way.