Delivering the book is difficult to do. You will have written, rewritten, polished and agonised over this book for probably well over a year - and that's if you are a quick writer. My books now take much longer. You will worry about whether or not it is as good as your other books, as good as it can be, whether your editor will be satisfied with it. But at some point you have to let it go. So you write a friendly email explaining that it's done, maybe give your editor a call to let her know to expect it imminently, and press send. This was what I did, on the 20th of June, with The Heart at War. Then, there is a moment when you don't quite realise the book is finished. Then, you feel a very tentative sense of relief and begin to realise that the labour that has consumed a large part of your energy for a large portion of your life is done. It's probably a good idea to celebrate in some way, despite your exhaustion, because this is an important moment. And also because your family and friends may not have seen you emerge from wherever you write for some time and might actually quite like to see you.
Anything else you would like to know? Just tell me and I'll try to include it here.