As you get better at doing an activity, your body adapts to doing it. A three-mile run that might have once caused you to keel over now feels like a simple stroll. The ten pushups you thought you’d never do have morphed into twenty without breaking a sweat. This adaptation translates into burning fewer calories, which is yet another reason to mix it up with new activities. So today, do something different. If you normally go swimming, try a bike ride. If you normally go for a walk, maybe try a run or a dance class. If you normally do twenty push-ups for resistance training, try a few pull-ups or sit-ups instead. Added bonus? Having to learn different activities focuses your brain as well.