If I'm concentrating on something I don't usually smile unless I am successful at doing what ever I'm doing. But whenever I talk to people I tend to have neutral face with a slight lean towards smile. Even on the phone.

However, when I've had a rough day I have had people come up and say SMILE! IT CAN'T BE ALL THAT BAD. To which I give a tight-lipped smirk that says "You don't know the half of it." But once a lady told me to smile and I straight up told her no. That was a bad day.