Is there power in positive thinking?

I do believe there is power in positive thinking for many reasons. I think people need positive thinking to make optimistic decisions in life and they also are determined to do make the necessary actions to make it happen. For example a professional boxer must have positive thoughts if he wants to defeat his opponent he must put those positive thoughts into action so he can be at his best to give it his all. Thinking positive also helps with those who are depressed because if they are always pessimistic they will never make the right decisions to be happy in life. Even some mental illnesses are due to excessive negative thoughts that could have been avoided if they just had some positive thoughts. I also believe that we need some voluntary actions to make the positive thoughts into power because nothing will change if we just think it but not put it into motion. The power that comes from positive thinking must be put into action for them to be used.