Go ahead. It won’t hurt you. It might actually make you happier, too. Based on the psychology that a person feels whatever emotion they are acting at the moment, you will probably feel better if you smile. To avoid what is called cognitive dissonance, in which our thoughts and actions don’t match up, our minds react to the change in our facial expression to bring our beliefs in line with our behavior. And, like laughter, it’s contagious. If you smile, chances are that those around you will too.

Source: www.time.com