Orange juice, generally. Oh, is that not what we were talking about?
One can only focus on a particular task for so long before mental fatigue sets in. Let's say that's about 30-45 minutes. After that amount of time, the brain needs to reset itself to keep going. It is during this short amount of time when you make that fatal mistake which costs you the race.
So the trick is, concentrate less. So when you're at a place that doesn't require you to be locked in to the screen, give yourself a rest. relax your eyes, look around the room, and completely disregard the race to rest your brain/reset. As you're about to start racing again, quickly refocus. You'll feel much more fresh and prepared to go another stint mentally. 👍