I know you are young and you feel like you're invincible. I know you can pull an all-nighter and work the next day just fine. We have all been in that situation and believe me, it is gonna take a toll at your performance ... and it could even trigger or help you develop some health issues in your life that can sabotage you down the line.
Realize there's only so much progress one can do in the day. Stop before you are absolutely exhausted and passing out, I know it's sounds tempting but please please do not fall into the trap management or more senior people (that were forced to do this too but didn't learn or are "paying it back" now negatively) to wrest that one last drop of energy. After your X allotted time, even if you are still feeling energized, go spend that energy jogging or something! Work a craft, learn to play an instrument.
Risking to toot my own horn, this might be the single best non-technical advice in this thread.