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