I just put in my notice this week! There's no better feeling than leaving a bad situation. It's like getting a regenerative phoenix moment after you've burnt out (hopefully you can avoid getting to that point). When I have left jobs in the past, I had a new thing lined up, but in another, I had no real plan whatsoever. Admittedly in that case, I had saved up enough to wing it for a bit, so it depends on your situation. For what it's worth, I have only ever regretted leaving one job, and I only left it because another place promised me more money.
