I used to believe that positive thinking is the key to a happy life. We've all heard it before -- try to look at the glass half full and you'll be happier that way. And who knows, maybe you can even "think (positively) and grow rich" or "attract what you want with (positive) thought wave," as well-meaning motivational speakers want you to believe.
I worked diligently on my thoughts. I did daily affirmations and tried all sorts of visualizations. They did make me feel better... for a spectacular half-day. And then I would fall back to the old me, like Cinderella after the midnight ball.