advice?

I just got back to chess last week after a year due to a burn out, I've been playing, studying for ~4-8 hours a day and sleeping late (due to the world chess championship). So in these few days I gained ~100 (1300-1400). But for the last 3 days I've realized my awareness has suddently gotten worse and I've been tired and blundering left and right like a 900 rated player because of the lack of sleep. I've heard getting to the high intermediate level (1600-1700) requires a lot more than just playing so I don't really know what's the most optimal way in studying, what to study, and how many hours I should play a day without feeling too fatigued. Like should I avoid faster time controls? Should I only play when I have higher energy levels?

Please leave a post if you can, thanks

Hi.

I am rated over 2400 online (https://www.chess.com/member/ppandachess). I created a free course that will teach you a training plan to improve. Feel free to check it out: https://www.panda-chess.com/daily-improvement-plan

Learn and apply the most important principles of chess. - (core of my teaching)
Always blunder-check your moves.
Solve tactics in the right way.
Analyze your games.
Study games of strong players.
Learn how to be more psychologically resilient.
Work on your time management skills.
Get a coach if you can.