I think the first thing is to establish why your current job is making you so miserable and exhausted, and what you can do to organise your day so that you are

I think the first thing is to establish why your current job is making you so miserable and exhausted, and what you can do to organise your day so that you are not left wrung out at the end of the day. Optimising your time and energy is a better option than quitting a job and dipping into your savings. Once you’ve worked that our THEN you can think about whether to quit your job. Because the problems you are suffering now are unlikely to go away if you make such a major and fundamental change in your life. They might - but they might get much worse. Working with a therapist or a coach might help you unblock whatever is holding you back and identify how to increase your energy and reduce frustration. That would be a better use of your savings - right now - than quitting your job. You also don’t say whether you have any experience on the business side of things. A side project supported by a stable job is very different to something being your primary source of income. I’m not saying don’t take the jump - but get everything lined up and address the disorder first.