Play, Play, Play
Believe it or not, there is a "happy zone" in your brain, and games can stimulate it. Card games, board games, guessing games, they all work, as long as you enjoy them. Physical play also lights up the "happy zone" in the brain, so grab a grandchild and go run around outside. And if you like sports, don't just watch, participate, because the fine-motor components involved in just about any sport increase happiness, too; apparently the rhythmic movement gives you a sense of mastery and control which increases your level of happiness. But don't think you have to play high-impact tennis or basketball to boost your mood — mini-golf, ping-pong, and even cooking and gardening work, too.