Since I'm a scientist and believe in an evidence-based practice of dentistry, I would like to share some science with you. In the book Mindfulness, An Eight-Week Plan For Finding Peace in a Frantic World, authors Mark Williams and Danny Penman site a study published in 1988.  The reference for the published paper is:

Strack, F., Martin, L. & Stepper, S. (1988), "Inhibiting and facilitating conditions of the human smile:  A nonobtrusive test of the facial feedback hypothesis." Journal of Personality and Social Psychology, 54. pp. 768-77.

This is taken directly from the digital book Mindfulness on page 103:

"the psychologists Fritz Strack, Leonard Martin and Sabine Stepper asked a group of people to watch cartoons and then rate how funny they were.  Some were asked to hold a pencil between their lips so that they were forced to purse them and mimic a scowl. Others watched the cartoons with the pencil between their teeth, simulating a smile.  The results were striking:  those who were forced to smile found the cartoons signficantly funnier than those compelled to frown.  It's obvious that smiling shows you are happy but it is, admittedly, a bit strange to realize that the act of smiling can itself make you happy...Smiling is infectious too.  When you see someone grin you almost invariably smile back.  You can't help it.  Think about that for a moment:  just the act of smiling can make you happy (even if it's forced); and if you smile, others will smile back at you, reinforcing your own happiness.  It's a virtuous circle."

So you see the smile is powerful.  Try smiling a bit more and see what happens.  Make sure your smile and body are both healthy with routine complete examinations.