Build up these things:
-A really awesome network
-A client/customer base
-Resistance to bullshit
I have wanted to be an entrepreneur since I was 23 years old but was tied to a full-time job for health insurance and income to pay off medical and student loan debt. In 2010, I decided that I wanted to start a blogging/content consulting company. By 2011, I was making $5K a year with my side business and by 2012, I was making 1/3 of my full-time income. In 2013, my side business amplified, and two weeks ago, I left my full-time job.
When I share this story, folks think that I accomplished some amazing feat, but I didn't. I worked my ass off -- 17 hour days for a year and a half straight. I networked relentlessly for client work and built a strong foundation to never have to rely on a full-time job again.
I think that your transition will depend on the type of business you're running. You'll need to develop your assets + client base. When you feel like you have a strong foundation and can support yourself financially, jump.