It has been determined that just going through the motions will improve your mood. When you're blue, just plant a smile on your face and see how long it takes until you are feeling just a little happier. Obviously, presenting a dour puss to the world isn't going to do anything for the people around you, but give them grin and you'll likely get one in return.
And of course, appealing to the vanity in us, it's a known fact that smiling is good for the face. Forget those worry wrinkles and go for the lift.
It doesn't matter what type of smile you wear either, I don't think. For example, the smiles we preserve in photography can be forced or genuine, formal or relaxed, coy or larger than life. We catch subjects in poses, in contemplation, in repose. Either way a smiling face, or one lit by laughter will transform a face only in the best way.
So speaking of transformation, I wondered what could be done to actually have a photograph make me smile. What I found were a number of tutorials to turn a picture into a cartoon. This is a relatively simple effect to achieve and should be guaranteed to turn a frown upside down.
Photo to Cartoon Effect
Turn Your Photo Into a Cartoon
Photo to Cartoon Photoshop Tutorials
Turning an Image Into a Cartoon Character