What a beautiful question that does bring a smile to my face. Just thinking about smiles makes me smile. Truth be told I am uncomfortable with this subject. One day I smile at my roses. The next I frown at them. Smiling to me is a mood and I wish I could keep mine at all times smiling.
Alas I am a man of no great discernment. So I will always smile inappropriately to the world as my happiness is contained. Strange this life, everything should make be smile, yet only my particular mood determines when I do.