Last year an Apple employee encouraged me to turn off my cell phone every day for at least ten minutes. She said, “Go brush your teeth, use the restroom, maybe take a shower, and then you can turn back on your phone. It will last much longer that way.”
That’s such good advice for how to do significant work.
You can’t work all the time. You need to shut yourself off every day. I recommend several times a day just shut your brain down. Go for a walk. Take a nap. Watch a mindless television show. Allow your brain time to completely ramp down.
Then when you come back do so with much better energy.