You may need to intentionally give yourself permission to take a break. Set a time for a couple of hours or set a particular date on your calendar (ideally, as a recurring event) where you will allow yourself to do nothing in particular, but rest and rejuvenate..
The tools in the Spirit, Mind, and Body chapters are all helpful for taking breaks from productivity. Setting a timer to meditate and just do nothing but have a blank mind, is a good way to take a break. Taking a walk with no purpose is another. Engaging in a sport for fun or getting some exercise just to make your body feel good, offers a healthy break as well. Calling up or meeting a friend can also be a good way to be non-productive and have some fun.
All those methods will give you a break from the “need” for productivity. Interestingly, though, when you get back to work you’ll often find yourself refreshed, better able to think clearly, and more motivated to get things done.