Today I had the pleasure of spending time with Catherine Iste. She is a fascinating woman. She likes to smile and offers us advice on this very topic.
It is physically easier to smile than frown. Even if you are not happy, your mood will improve just by smiling.
But before you head over to YouTube or the latest Dilbert, stop. Research shows you don't need to do anything but form the smile on your face and your mood will improve. Try smiling; eventually your mood will catch up with your face.