If smile like you mean it you will be really happy. But many people smile because they have to. I have one example. In ancient times. Clowns always laught but they are not happy at all. Clowns always had facepaint with a big smile on it or wore a big-smile mask. There is a proverb about it: Clown’s masque smiles happier than anyone, but the clown can’t not hide his tears in eyes. Nobody know how lonely and sorrowful a clown is. Clown work so hard to make other people happy. When the clown put a big smile on his face and make audiences happy, they cry inside of them.Yes, the audience smile like they mean. But the clowns, they never smile like they mean.
I believed not everyone smile like they mean to. Sometimes people have to smile because smile is a masque that can hide sadness.