Think about it. Having your book in on time is not just for one person. You have many other departments that require your book to pass through their hands. Your editor has to really look it over one more time (along with all of her other authors). But more importantly, you have readers. Keeping your name out there on the book shelves is one of the biggest keys to success. It's all about name recognition and you simply cannot do that with only one book.
Successful writers have been using these deadlines during their entire writing career. They used deadlines religiously during their unpublished life. The question is, are you? A writers simply cannot sit around and wait for someone to create a deadline to have something produced. It takes a personal discipline to say, "I will have X project finished by this date." Even more so, the disciplined writer will work with smaller benchmarks during the writing process:
- I will have the proposal sent to X by this date.
- I will have the first three chapters sent to CP by this date
- I will have the first half ready for editing by this date.
There are no "...but's..." with deadlines.
So, if you haven't started yet, start today. Create those deadlines and stick to it.