Believing in yourself can help you hit the clutch shot, score the promotion, get the girl. But did you know it may extend your life, too? Researchers at the University of Canterbury in New Zealand performed a series of experiments with 184 participants. One study provided false feedback about intelligence or personality to raise or lower self-esteem, while another had participants rate their own self-esteem over a two-week period. The researchers then checked each participants’ “cardiac vagal tone,” a measure of how strongly the parasympathetic nervous system affects the heart. The PNS can reduce stress and inflammation as well as the risk of cardiovascular problems and autoimmune disease. The overall study, published in the October 2010 issue of the Journal of Research in Personality, found a correlation between high self-esteem and high vagal tone, the first indication that confidence can affect your health. Which is why we say: Work out like a champ, believe in yourself … and your body will, too.