Mounting research shows that optimism could extend your life. The latest study comes from Wageningen University in the Netherlands. For 999 elderly Dutch men and women, agreement with statements such as “I still have many goals to strive for” was highly predictive for longevity. When subjects were traced nine years after being surveyed, death rates of optimistic men were 63 percent lower than those of their pouty peers; for women, optimism reduced the rate by 35 percent.

The Dutch study also begins to map out causality. By controlling for dietary factors, smoking habits, obesity, physical activity and alcohol dependence in participants, researchers isolate optimism's protective influence. Some of that influence drives healthy behavior. “Optimists will try to avoid and escape bad events,” explains Martin E. P. Seligman, a psychologist at the University of Pennsylvania not linked to the Dutch team. For example, they are more likely to follow prescribed medical routines.

Fortunately, pessimists can learn to look on the bright side. In a study by Seligman, pessimistic college students randomly assigned to optimism workshops subsequently had fewer visits to their school's health services department and had lower rates of depression and anxiety than classmates who had no happiness classes. Positive self-talk can help, too. For example, says Robert C. Colligan, professor emeritus of psychology at the Mayo Clinic, “a student with a bad grade should replace ‘I’ll probably fail all of my other courses, too’ with ‘It’ll go better next semester.’”