Because positive thoughts attract positive things into your life, whereas negative thoughts won't help in any way, they just put you down. When you have a negative thought, try to stop it or transform it into a positive one.

Positive thinking is a way to find solution out of difficulty and keep self moving forward to success. I sometimes use negative thinking to reflect on what I need to do more to improve my performance.

a positive people live longer :))

Because it makes me happier!