When I walk past strangers, whether its in the office, on the streets, in the subway station., etc, I never know what to do with my mouth.

All the material I read here suggests to make eye contact and smile. I have no problem making eye contact, but I always end up doing a half smile / grin without showing teeth. Kinda like this, minus the good looks. For some reason, it just feels out of place to flash a full on smile.

Am I just being dumb? What do you guys do? Thanks.