When I was a kid, this man in my father's church would corner me and my sisters, tease up the sides of his lips with his index fingers, and bare his teeth: "Smile, girls, god loves you."
Not much about my childhood made me want to smile.
I grew up home-schooled and religious; I never felt like I could please my parents; I had zits and glasses and crooked teeth.
In my teens I became addicted to French fashion magazines and Kafka and Goodwill. Smiling was still unnecessary: I had pointy shoes and orange permed hair and a bad attitude. Smiling seemed like an invitation to talk to me and I didn't want people talking to me (see: homeschool) and I really didn't want them looking at me (see: skin + teeth + glasses).
These days I smile more. Reluctantly. Sometimes purposefully. A smile is so much. An invitation. A flirt. An acknowledgment. Relief. Divertissement. A precursor to a conversation, or a kiss, or punctuation to a goodbye.