At the first sign of sickness, Jenny Spring, 29, of Cambridge, Mass., practices another tactic linked to good health: “I tell myself that I refuse to be sick.” Is she crazy to think that works? Not at all. In one study, participants who had heightened activity in a region of the brain associated with a positive attitude produced greater amounts of flu antibodies. Another study showed that people with sunny dispositions churned out more antibodies in response to vaccinations. Researchers aren’t clear on the connection, but they do know “the brain communicates with the immune system, and vice versa,” says Anna L. Marsland, PhD, director of the Behavioral Immunology Laboratory at the University of Pittsburgh. And a growing number of psychologists stress that focusing on wellness, as opposed to illness, can have good results.

Make positive thinking work for you: If you don’t always think positively, experts say, you can at least learn to be less negative. Don’t dwell on your symptoms when you do get sick, and try not to assume the worst (like telling yourself, “I always get sick this time of year” or “This cold blows the whole week”). Practice focusing on your strengths and how you feel when you use them. Slowly, you’ll recognize that these feelings are more rewarding than negative feelings. “You probably can’t change your personality,” Marsland says, “but you can change your behavior.” Odds are, you’ll join the ranks of the perennially healthy.