Struggling through your workout? Here's a quick and easy way to re-energize.

Relax your face and smile. I know -- when you're trying to bench half your body weight, the last thing you probably feel is happy, but research shows that smiling through the pain is an instant way to improve your mood and help you feel more energetic.

Why? Well, it's simple, really. The look on your face is strongly connected to how you feel inside. So this goes for everything you do in life. Rushing around the grocery store? Smile. Cleaning the floor? Smile -- and put on some good tunes. Getting your legs waxed? Well, smiling might not take away the pain -- but it can't hurt!