Ive heard a similar idea, from Hemingway. "Learned never to empty the well of my writing, but always to stop when there was still something there in the deep part of the well, and let it refill at night from the springs that fed it. I always worked until I had something done, and I always stopped when I knew what was going to happen next. That way I could be sure of going on the next day." — Ernest Hemmingway"

I really agree, and I also thinks it can be helpful to do something similar when taking breaks (have lunch/take a walk while leaving a failing test).