Days off are hard to judge sometimes. Should it be a day of fun--filled with activities? Should it be a day of rest and relaxation? It takes time to learn what you need. Most of my days off are a little of both.
Unless I have some grand adventure planned for the day, I allow myself the pleasure of sleeping in as long as I want/need to without feeling guilty. Then I take my time getting up, reading, and general putzing. At some point I'll take a shower and get ready for the day. This is generally followed by an attempt at some productivity which inevitably fails. I do eat. I might nap. I might go for a walk, but whatever I do, I allow myself the privilege of doing whatever it is that I feel like doing. I usually spend at least part of the evening with friends over dinner and then I make my way back home and play on the computer before going to bed.
There's something very special about only having one day off a week. It challenges your priorities. It makes the time more precious. It's just weird that it's Monday.