What makes you smile till your cheeks are sore? :)

Why is it that when a person smiles at someone else, it is often found that the person who was smiled at, smiles back. Mabe its because smiling is so contagious and beacuse smiling is fun :)  A smile is the most simple, inexpensive and most wonderful things in the world. Not only does a simple smile release happy endorphins but it can make someones day, who may have been having a hard one. Come on :) why dont you give it a try- close your eyes and smile as wide as you can and see how it makes you feel and what thoughts come into your head. These images are most probably perhaps someone you love, a joke you may have heard, a memory of a holiday, a special gift that was given to you, or mabe a movie you once saw or even that contagious laugh of someone you know! :). I know that when i have had a rough day there are people i think about that no matter what make me feel better just by thinking of them. So guys what makes you smile till your cheeks are sore?