Runners know the feeling: you've made it halfway through, and those endorphins kick in, and you feel like you could go forever. What began as something you had to push yourself to start becomes a true pleasure. Well, it turns out that exercise, like running, can actually help relieve anxiety and depression. Scientific studies have found that exercise can increase the levels of serotonin as well as endorphins in your body. These naturally occurring chemicals can help decrease feelings of sadness, anxiety, and pain, along with increasing your sense of well being. It's true, when you're feeling down the last thing you might feel like doing is working out, but studies have shown that any activity, from walking around the block to yoga to biking can help. Rather than reaching for the pill bottle, or in additional to taking doctor-prescribed antidepressants, think of exercise as another way to boast your mood and your wellness. Write yourself a "prescription" to take a short run or walk, get on your bike, or go to the gym. Your body, and your mind, will thank you.