Looking at my journal* (personal work journal), it went like this: Tuesday: came up with idea. Wednesday: had dinner with previous startup CEO who I remained friend with. He expressed that it was a good idea and if I wanted to learn the pain of startup for myself, I should do it. Thursday: thinking... lots of thinking--then I came to a conclusion: it must happen NOW! Told my work people and they were very supportive. Friday: I left the company on good terms (the company told me to come back once I have my product developed, they'll be the first customer).
2 things I believe in: 1) you do it because you HAVE TO do it--you cannot live without it. 2) you're always about a few years late :P
With that being said: 1) I am married and my wife and I had some cash to sustain us for a few months so I do have a bit of a nest and health insurance is on the wife 2) My idea is very simple and I believe it can be accomplished within a short time. 3) I cannot live without doing it (living without passion is simply surviving)
If you truly believe in your vision, then you should have no problem laying your life down for your vision. If you are willing to put your life on the line, then like Scar Face "the world is yours"
Good luck, friend and always, fight like hell.
PS: *One condition the wife gave me when I quit was I have to keep a daily work journal. It's very helpful. My recommendation for you is to keep a journal--you will read back on this as perhaps the most enlightening self reflection. You don't have to write all thoughts, just what you did that day and the tasks will tell you what you were thinking.