A few notes form "Life 101":
If you have the choice: Don't quit your day job until your hobby is generating a significant portion of your income, and the opportunity is identified to increase the hobby's income enough to support yourself and grow the business.
Across the years I have ruined some perfectly good hobbies by trying to make a living at them. It always seems like the demands of the market place require doing things that aren't as much fun as the challenges of the hobby. (paper work [lots of it]; dealing with people [irate, stubborn, dead beat, mean, picky, etc.] and doing it with a smile; not leaving the unresolved problems on the shelf until you are ready to deal with them -- if ever, etc.) It helps to know about these before you take the big leap.
I only need for my hobby to pay for its self. At the moment it is doing a bit better than that, but I don't know what happens after the current cash cow runs dry. There can be a lot of hit and miss before you find the products and outlets that will work for you. What Shadez says about having more than one way to generate income --that is a big deal. The more you can do, the better you chance of success.
You will be trading the relative security of a steady pay check (and perhaps a benefit package) for the uncertainty of how you will pay next months rent.
From my perspective, the biggest key to success is to do something you love so much that you are willing to go with out sleep or food to do it, and still want more. It must also motivate you enough that "all that other stuff" doesn't really matter. That also helps with the "confidence in yourself" thing.
Best of luck, what ever you do,
Klahr