How do you deal with having to pretend you're happy when you're not?

Real life: We all have to be in certain moods different than how we are feeling inside. Do you think all the cheery clerks at a retail store, have had a great day? It is part of our equipment as a social being, and an important part of dealing with our children, our friends and colleagues. And maybe pretending to have a cheery outlook can be catching to you as well and you will start to feel better.