FEAR IS GOOD; in emergencies, it enables us to fight or flee. But often we get scared at the wrong time—when we step onto the field for a big soccer game or up to the microphone at a contentious town meeting. Professional athletes and actors say some nervousness helps them concentrate better. But when performance anxiety is too powerful, it undermines our efforts: a player's legs become wobbly, a violinist cannot find the correct notes, a manager in a meeting forgets all the talking points. Survival may not hang in the balance, but social, professional or financial success can seem to be in grave danger.