Sitting around, or goofing off without doing anything strenuous will take you downhill fast. On days that I don't do anything productive I always do some push-ups, sit-ups, and swing some dumbells around a bit. If I don't I will start going soft fast.
Love riding my bicycle but I'm tired of all my trails around here, need to find, or make, some new ones. Nothing clears out my lungs and makes me feel better than a 3-6 mile bike ride. All of this holiday food consumption isn't helping me a bit.