Take a break
Some days it is simply time to take a rest. I have long been driven to accomplish something everyday and I find it difficult to just stop. I used to work for a large credit union in their mortgage department. Things were very stressful for a long period of time and I had two ways of de-stressing. Most days I would leave my desk, walk downstairs, get a snack and read the business section of the paper for ten minutes. Many people would not see reading the business section as relaxing, but it worked for me.
On those days that were extremely stressful, I had another trick. I would go outside and walk around the building, sometimes twice. It didn't take long and wouldn't really count for exercise, but the fresh air and the little bit of exercise did a lot for helping me to relax a little. I was able to return to my desk calm and refreshed, ready to work again.
Now, my lifestyle is much less stressful and I have a lot more control over my time. Unfortunately, the task master in my head is still relentless. The downside of having more control of my time is that I don't think of "lunch" or"break" so am not as inclined to stop for a bit. Learning to give myself a break is more about learning to be kind to me. Some days It is okay to stop, relax and simply enjoy the day.