Grinding, fretting and brooding? How do you unlearn it?

Imagining improbable disaster scenarios when you just want to relax. Or mulling over ways in which tomorrow's presentation could go wrong just as you're trying to fall asleep. We all worry sometimes. But when it grips you day and night, you may be overdoing it. Psychologist Bart Verkuil tells you the key to a life with less worrying.