I feel you, IslandFIGirl. I'm planning on doing something pretty similar in the next few months, and in my head the panicked mutter of "what are you doing? what are you doing??" is only matched by the running refrain of "get out get out get out." In my case, there's nothing even particularly awful about my job or the people in it, I'm just-- done and ready to get the hell out. As a usually risk-adverse person also taking a huge leap of faith and wondering if I'm about to make a terrible mistake, I FEEL YOU.
At this point, when you're committed to leaving, the next best thing to do is start prepping for where you'll land next. Make a plan, set a timeline, and stick to it.
Brainstorm on what actions you can take to make your post-job landing easier, and to turn the ship of your life in the direction you want. Whether it's cranking up the savings rate to maximum and turning the spending rate all the way down, blowing the dust off old professional relationships and polishing up the networking engine, researching other companies and roles you'd like to work in, think about what's going to make YOUR life better six months, a year from now, and start working toward that goal.