I was in the same boat 14 months ago: worked as a corporate attorney at a top tier firm, folks were actually really cool and the pay was ridiculous. Oddly enough, even my hours weren't that bad. So I knew I had a lot to be thankful for.
But I wasn't thrilled about my job. I didn't feel proud when I told strangers what I did, and that really got to me. I wanted to work on something that I cared about, and I wanted to try my hand at risk, learn some new skills. I also had zero interest in turning into those who were above me at the firm.
So I quit with almost no plan, and I ran a startup I created out of thin air, Trendero.com. It launched, it worked, and I saw a bright future stretch out before me.... Thing is, it actually still hasn't taken off. I haven't made a dime from the idea, and now I'm looking around at BD roles with other startups, since I've basically burned through all of my savings.
That all being said, I'm happier, prouder, healthier than ever before. I fought some battles, lost a few, made some awesome new friends. And I'm proud to talk about what I've done, happy to wake up to my new, much more frugal life.
So do it, screw the plan. That's the story you'll want to tell your grandkids.
Caveat: I have no kids, no wife, no dog, no mortgage. I knew the window was closing for me to do this kind of thing when I quit, which was largely why I made the decision. But if you have other burdens/responsibilities, think a bit more carefully. Chances are, you will be substantially poorer for a while.