Then the real writing begins.
I tell my daughters that all the time. The first draft of a book should be flown through like a jet at Mach 5. Just don't expect it to be done. Writing is re-writing as someone once said. If you go into that knowing your first draft is basically just a pencil sketch, you'll be much more acceptable of the prk the second through tenth drafts will take.
But write on. Always write on.