Living in New York invites a lot of chaos and conflict. Someone on the subway calls you a "fat-ass." That man certainly did not appreciate you asking him to turn his music down and has called you a word unfit to print. Strangers comment on how you raise your kids. Strangers's kids, um, comment all over your purse.
Inevitably, words are exchanged, and if you're me, you have the perfect comeback ... 10 minutes later.
Has that ever happened to you? You get into it with someone, they insult you, and instead of having that perfect scathing response you say something like "well, well, you're mean!" And then it gets under your skin and you fume and huff and spend the next hour, day, week re-imaging the exchange. This time, you are quick. You are a verbal ninja. You stand cooly and shut-down your opponent. You fantasize about the fight, expand it, condense it. You imagine the shining moment where you win - hands down- whatever exchange it was that left you feeling small.
That's sort of what drafting your book is like. You want to have the perfect scathing response and instead you write "It was a Dark and stormy night."
I suspect the main reason that people who wish to write, but fail to write, do so because they want write well. You must, first, be willing to write terribly. If you want to write a book, your goal should be to write a book. Not a good book. Just a book. Worry about the "good" part later.
If you haven't read Annie Lamott's Bird by Bird go do it right now. Seriously, get off my blog and go read that book. Ms. Lamott is a huge believer in "the shitty first draft." She argues, rightly if you ask me, that a first draft is just for getting it out of your head an onto the paper. It's sort of meant to be bad. Just get it out; word vomit! You don't even need to show anyone (certainly don't show your agent ;). It's just getting the bones of your story on paper.
Once you have that version done (and most people don't get THAT far) you can start to worry about being good. You can start imagining the draft where you win.
It's going to be a while. This is the stage where you're figuring out what you should have said; what you meant to say. Slowly, you're winning this argument.
Then there's the 3rd and 4th and so on drafts. These are for figuring out how to say what you meant to say. How to bring your voice to to the novel.
Some very lucky, very skilled people, are good at getting a near perfect first draft. Just like some very lucky people are quick with the perfect comeback.
But for mere mortal writers (and fighters) accepting the imperfection of the first draft, and just aiming for completion of the first draft is going to the best way to start. Baby steps.