Editors’ note: We’re resurfacing this story from the archives because who wouldn’t want to master their emotions?

LAST month, in San Jose, Calif., 21 people were treated for burns after walking barefoot over hot coals as part of an event called Unleash the Power Within, starring the motivational speaker Tony Robbins. If you’re anything like me, a cynical retort might suggest itself: What, exactly, did they expect would happen? In fact, there’s a simple secret to “firewalking”: coal is a poor conductor of heat to surrounding surfaces, including human flesh, so with quick, light steps, you’ll usually be fine.

But Mr. Robbins and his acolytes have little time for physics. To them, it’s all a matter of mind-set: cultivate the belief that success is guaranteed, and anything is possible. One singed but undeterred participant told The San Jose Mercury News: “I wasn’t at my peak state.” What if all this positivity is part of the problem? What if we’re trying too hard to think positive and might do better to reconsider our relationship to “negative” emotions and situations?

Consider the technique of positive visualization, a staple not only of Robbins-style seminars but also of corporate team-building retreats and business best sellers. According to research by the psychologist Gabriele Oettingen and her colleagues, visualizing a successful outcome, under certain conditions, can make people less likely to achieve it. She rendered her experimental participants dehydrated, then asked some of them to picture a refreshing glass of water. The water-visualizers experienced a marked decline in energy levels, compared with those participants who engaged in negative or neutral fantasies. Imagining their goal seemed to deprive the water-visualizers of their get-up-and-go, as if they’d already achieved their objective.