We often have non-park days during our trips (the longer the trip, the more non-park days). Sometimes we'll stay at the resort and have a VERY lazy day: sleep in, late breakfast, stroll around the resort, swim, soak up some rays, read, nap,.....
Other times we'll do a bit of that and then leave the resort for something else: golf, DTD, water sports. Maybe a dinner show in the evening. Things you're too tired to do after a full day in the parks. It's a great way to recharge after a few hectic days of park touring.