Editor’s Note: We’re resurfacing this story from the archives to show you why positive thinking may be overrated.

MANY people think that the key to success is to cultivate and doggedly maintain an optimistic outlook. This belief in the power of positive thinking, expressed with varying degrees of sophistication, informs everything from affirmative pop anthems like Katy Perry’s “Roar” to the Mayo Clinic’s suggestion that you may be able to improve your health by eliminating “negative self-talk.”

But the truth is that positive thinking often hinders us. More than two decades ago, I conducted a study in which I presented women enrolled in a weight-reduction program with several short, open-ended scenarios about future events — and asked them to imagine how they would fare in each one. Some of these scenarios asked the women to imagine that they had successfully completed the program; others asked them to imagine situations in which they were tempted to cheat on their diets. I then asked the women to rate how positive or negative their resulting thoughts and images were.

A year later, I checked in on these women. The results were striking: The more positively women had imagined themselves in these scenarios, the fewer pounds they had lost.