One of the greatest things about your body is that it responds to what you're doing through mechanisms called feedback loops. You tell your body that you want to watch reruns all night, and it responds by downshifting energy production. But tell your body that you need to walk around the neighborhood or swim a few laps or do an early-morning stretch-to-the-ceiling routine, and it responds by giving you the energy you need.
Take advantage of these feedback loops by integrating more exercise into your routine. And start early in the day, when you have the energy to exercise. Ideally, aim for 45 minutes a day of physical activity with at least 20 minutes a day involving the sore muscles.
Start by doing gentle exercise such as walking or warm-water stretching. The trick is to do only the amount or intensity that makes you feel "good tired," not "bad tired" or in pain afterward. Tell your body which way to go, and it's going to follow.