A recent article in the American Journal of Cardiology based on a study conducted at John Hopkins came to the conclusion that "If you are by nature a cheerful person and look at the bright side of things, you are more likely to be protected from cardiac events."
The lead author Lisa R. Yanek states "A happier temperament has an actual effect on disease, and you may be healthier as a a result."
All the more reason to say "Don't worry, be happy"