You write another book. And a book proposal. And a book synopsis. And put in the edits for all three. And again. One more time. And send it again and think "Whew! I did it." And don't be surprised when you get an email exactly seven minutes later with more questions, concerns and revisions.
And so it begins again. With every novel that has a chance of a paper printing, there are these steps. And remind yourself that most authors go through them. Most of us aren't a Grisham or a King. But most of us would give almost anything to be.
And is it worth it?
It had better be. If it's not, then you shouldn't be a writer. Learn to knit. Train for a marathon. Do something--anything--other than writing.