In a study of more than 1.2 million Americans, they discovered physical fitness is more important to your mental health than how much money you make. To be exact: exercisers are, on average, depressed 35 days a year; for non-active participants that number is 53 days.
Researchers found that physically active adults self-report feeling depressed much less than couch potatoes. They point to the fact that exercise is correlated with numerous health benefits, including reduced risk of overall mortality, cardiovascular disease, obesity, stroke, and cancer.
If you feel good, your perspective tends to follow.