I'm a programmer. I am always angry at job. Is this normal?
teralaser: Did you ever pick up a (personality) trait or habit from a co-worker, although you didnt want to ? 
Did you ever have trouble understanding how a policeman ignores obvious insults and stays cool ?
Feelings are catchy like the flu, but remember you are a part of the equation too. If you treat a desperate customer with calm and being realistic, or colleagues with humor and a relaxed mood, they might catch it too.
So there is a starter strategy, although it might take patience.