A prophecy predicts the future; in a self-fulfilling prophecy, the words themselves cause the “prophet” to change his behavior and make them come true. For example, someone who declares that “this is going to be a horrible day!” will be of such a foul mood that he sees nothing but bad things—and possibly react negatively to everything. An optimist who says “this is going to be a great day!” sees nothing but good things and turns crises into opportunity.
One of the most famous examples of self-fulfilling prophecy is the Greek mythological character, Oedipus. An oracle declared he would kill his father and marry his mother. He is sent off to avoid this fate—but in the process of running away from, it sets off a chain of events that makes that very prophecy come true. (Or, for a more modern example, there’s Harry Potter. Voldemort attempted to kill the baby that a prophecy said would destroy him—but in that attack, transferred some of his magical abilities and empowered a probably-very-ordinary-child to become his greatest nemesis.)
The actual term “self-fulfilling prophecy” was first used in the twentieth century, coined by the sociologist Robert Merton and included in the book Social Theory and Social Structure. Merton believed that all prophecies are possibilities, but one’s unconscious or conscious behavior makes them probabilities. In other words, the future is not made by fate but by attitude or perspective.
“Self-fulfilling prophecy” has been used, in some extent, as an approach for treating anxiety disorder and even chronic pain, thanks to breakthrough studies that show the effect of perception on reducing panic attacks and even pain episodes.