I don't know what famous author said that but, boy, do I completely agree.
I used to think that the best part of writing was getting caught up in a new story idea and then brainstorming/outlining/imagining/daydreaming/insert your favourite word for doodling out the next big concept that would consume you for three to six months here. Then I thought that the best part of writing was starting the first draft when everything was bright, shiny and new. Then I thought getting to the end of that first draft was nirvana. I must say that never once did I think slogging through the morass of the middle was the best. Still don't. But murky middle notwithstanding, those other things are pretty cool.
But now, I really believe that having gone through all those steps, the outlining, the beginning, the dreaded middle, the blissful end, the seemingly neverending revisions are simply teasers until you get to the very best part of the writing process - the knowledge that you have finished. It's kind of like licking through all that hard candy before getting to the soft, chewy centre of the Tootsie Roll pop. That feeling when you can sit back, read through the entire novel - my God, I've written an entire NOVEL - and bask in the thrill of creating something that you are (hopefully) proud of, something that (hopefully) hangs together, something that (hopefully) has the layers and the meaning and the subtext you wanted to convey to a reader, is like no other feeling when writing.
It is all that is good and satisfying and fulfilling.
Yes, I know that a book is never completely done. Yes, I know that should the book sell there will be still more to do. But, for now, it is enough to know that I have written. I have reached the soft, chewy centre of the Tootsie Roll. And, no matter the consequences I might have to face later, I'm sure as hell enjoying the decadent sugary high of it now.