At the end of Feb, I will have gone one year without a job. By choice. I spent that time finishing grad school and working to get some things off the ground.
I used to have cold feet and sometimes I really hated my own guts for throwing my savings away for what felt like "spinning my wheels". I was also afraid of losing my bargaining power/credibility in my old community the longer I spent time away from it (unfounded fear FYI). Oh and I had months where I felt like I wasn't making progress fast enough and I had many days full of questioning myself. I should note I launched two projects during this time that saw very little interest--finding this out early is a great argument for release early, release often.
Anyways, there is a happy stop gap in here somewhere. I launched a project in November and it gained interest and started making money. The profits are nothing huge but making that first $1 is huge to developing that entrepreneurial confidence. Its a small milestone but celebrate it anyways.
Now I'm getting close to ready with my big startup effort. Its based on one of the aforementioned failures but I'm using the lessons I learned and I'm really excited about it.
It took awhile but after a few breakthroughs I'm glad I took the jump. If I don't succeed now, I feel its certain I will later. Each effort I'm learning different things and starting to develop a mental model of what works and what doesn't.
Its one thing to read "write to bloggers to help market your product". Its another to write to them get zero response, refine your pitch, add a mediakit, and then try again and succeed.
My point is--you may have some growth to experience before you're ready to run a successful company. However, no matter how much growth you've got to go through, you may as well start now. It doesn't happen on its own.
Oh last point--to quit your job is a decision only you can make. I find when my personal needs are met its hard to force myself to do things that are painful but necessary for growth (i.e. get started). Even when I had significant savings left, I still felt too comfortable. Seeing my savings dwindle offered a great kick in the ass to move :)
I'm consulting now to meet my financial obligations but am nowhere near comfortable. This makes the whole thing feel like a "mission" and I love it. YMMV.
Good luck!