I quit an exploitative workplace about ~7 years ago, totally unprepared (and in a foreign country), and barely survived until my business picked up enough work to be stable. Spent all savings I had, even had to borrow a bit at the end to keep me afloat.

Hard work and persistence wasn't enough - there was a big element of luck involved, and things could have easily crashed and burned. It took me almost a year until I felt "safe". The transition period was very stressful, burned out a few times, and almost "gave up" (meaning, just go work for another company).

As others have noted, I suggest keeping your job, take time to prepare the ground, and make sure you're well-prepared for the transition. That means, have a profitable business before jumping ship. I know that's not easy (well, nothing worthwhile is easy), working full-time while building up a side business, especially if you're burned out at the current place of employment.

Another point I'd like to note is that "being your own boss" comes with its own challenges, risks and downsides. In a way, it's like working for many "bosses" (clients) without the benefit of financial security. So I would recommend keeping the option open to find a job at another employer, one that treats you better than the current one. If peace of mind is what you seek, that might even be a smarter choice.