Happiness is a decision. It is common for one to get angry, scared, sad, depressed, worried etc. Such emotions are normal for a human. It is up to one to decide whether he/she wants to be happy or sad. My take is that one wastes the time when he/she chooses not to be happy. The ability to put down the negative thought is one of the ways to the route of happiness.
Life is short. It makes sense to be happy at all times.