Things to do before you leave your current job: - make LinkedIn connections with all your co-workers. Generally co-workers accept those, even if they don't think you're great. The reason for this is to increase your number of "1st/2nd/3rd connections" on LinkedIn. Which likely doesn't matter, but hey why not. - Depending on where you live, you may be able to get unemployment if you quit or fired but not the other way around. So figure that out, as well as what health care looks like for you and plan accordingly. - Update your resume with your current projects etc. if you haven't done that lately.
Now once you are free of your current job, don't do any coding for a few months. No interview prep, no learning AI, none of it. Exercise and eat right, as others have said. Have a routine and maybe explore those 2 non-tech things.
But give yourself a calendar and come back to things after you've let the burnout fade a bit. Don't rush back after a month because you start to get anxious - your body physically needs to recover.
At this point, like it our not, I'd spend time getting comfortable with Cursor and vibe coding tools. Build a thing, see how it works, play around. You won't be able to avoid AI so see how it can help you with what you already know how to do and where it can't help.
If you suck at interviews and leet coding, don't worry about it. Take some interviews, bomb them. The goal is to develop a thicker skin, which is the first step. Also, if a company's hiring culture is steeped in crap you hate, you will probably hate the job anyway. If they as you to do a weekend project, prefer to do that. That is likely where you will shine. Plus, it is a good way to practice when unemployed.
Lastly, lean into your strengths - generalists and graybeards tend to be great at startups because they can pump things out and understand the big picture. Look for roles on sites like WellFound rather than LinkedIn. If you use LinkedIn, really only jobs through recruiters bear fruit nowadays.