Behavioral changes might actually influence your state of mind. Acting positively and not expecting the worse or considering that all people meant the worst thing possible when they say something may do wonders in one's life. Taking an ambiguous situation and putting it in a positive light might actually increase one's charisma and make one seen as inspirational. It might also help with problem solving skills.
Studies also show that optimism leads to longer life spans, lower stress levels, higher motivation, and better health.