I think I am going through burnout.
How do I deal with it?

Joined a startup with crazy work culture in Jan.
Have been working 14 hours a day for months starting march 2020, and even that was only to barely keep up with my colleagues. I have been one of the top performer in my previous jobs.

since the beginning, It always bothered me seeing people working on weekends, and falling behind if I didnt, to not have time for anything else, but I started really hating it a couple of months back.

Work has slowed down a bit now, but I just can't do it. Cant focus and get even basic tasks done. Still getting by with last minute efforts but I hate it!

Dont have the guts to leave the job, but also realise I am not doing enough and will get kicked out eventually anyway.

What can I do, to get over this?