I have a wonderful friend who said to me once (when I was moody & feeling sorry for myself) " Cheer up you big fanny!!". I first thought "You cheeky...." then I started laughing & really laughed. If I feel low I think to myself "Cheer up you big fanny!!"
When I'm moody I just go out for a long walk or a run and I immediately feel better and more positive. Endorphin high I guess?
Other things that cheer me up are jewelry, a nice big plate of pasta, and a good stiff drink.