Never pass up an opportunity to take a day off and RECHARGE, especially if you can do it outdoors!
There is a reason that no professional sports have their players competing in a game day in and day out. Without breaks between games players would burn out, would suffer more injuries, and would never have time to practice and get better. No matter how much we love what we do and how many hours we think we must work, the reality is that the more opportunities we take to not be buried in our work, the more we seek out and find an hour or two each week to let ourselves recharge the better we will perform.
You cannot give 100% week-in and week-out, you need time away from work to recharge. In fact pushing yourself to get work done for an extended period of time will actually produce less and at a lesser quality than if you cut back and spent a little more time away from the rush of needing to always be in production mode. Now, the best way to recharge is to get outside, go to a park, soak in the beauty of nature, take deep breaths and let your mind be free from deadlines and the office for a change.
Start setting aside a few hours every week to get away from the job and out in nature!