I can't think of a good title...

Sometimes customers come up to my register with a bad attitude. They get frustrated over the cost of a prescription or something else that is equally out of my control. Sometimes they get angry at the credit card machine because it asks for their pin number several times. By the third or fourth time they are literally pounding the machine with the stylus. It's pretty hilarious. Yet, no matter how angry or frustrated some people get, a lot of them still manage to give the me the most genuine smiles and pleasantly say "Have a nice day!" at the end of the transaction. It surprises me every time. I wonder if they feel guilty for getting mad at me or just really hope that, although they aren't having a nice day, that I will. I just don't know.