In fact, your thoughts often have much more to do with how you feel than what is actually happening in your life.
This isn’t a new idea. Nearly two thousand years ago the Greek philosopher, Epictetus, stated that people are disturbed “not by things, but by the views we take of them.” In the Book of Proverbs (23: 7) in the Old Testament you can find this passage: “For as he thinks within himself, so he is.” And even Shakespeare expressed a similar idea when he said: “for there is nothing either good or bad, but thinking makes it so” (Hamlet, Act 2, Scene 2).
Burns M.D., David D.. Feeling Good: The New Mood Therapy