It depends on the situation. In high school, my teachers would tell me to keep smiling and how nice it was to see a smile on my face. Working as a server, you have to be pleasant to the customers...but you can tell the difference between a "rehearsed" smile and a genuine smile. I have been known, on occassion, to b*tch out the kitchen staff, and then turn around with a smile on my face to greet customers.
Also, I'm usually smiling and laughing when I'm with my friends. I will come home and my cheeks will hurt from laughing so hard
Stephanie