Why smiling is good for you

When I was younger, I would consistently make fun of my mother for smiling so much. My mother--if you do not know her--has one of the biggest, brightest, most beautiful smiles that could warm your heart and turn your day around. I would tell her that she smiles too much and sarcastically ask why. Despite the ups and downs that my mother has had in her life, you'd never be able to tell because she always looks happy...and I mean ALWAYS. Through trials and tribulations, through her recent encounter with Breast Cancer and through the crappiest of times she has kept that smile on her face. When I was younger, I didn't understand why.