"The human mind is automatically attracted to the worst possible case, often very inaccurately," says Martin Seligman, who founded the field of Positive Psychology and runs Penn's Positive Psychology Center. "Catastrophizing is an evolutionarily adaptive frame of mind, but it is usually unrealistically negative."
To refocus the mind, Seligman suggests a simple exercise called "Put It in Perspective," which starts by conjuring the worst-case scenario, which our minds tend to do first, then moves to best-case scenario, and finishes with the most likely scenario. The idea is to redirect your thoughts from irrational to rational.
