John Cleese in his book about creativity talks about how procrastination is actually our natural ability to be most creative. If we are leaving something until the last minute, it often means we don't really have a great solution or don't have enough time to think about it. Even if we do have a solution in mind, leaving it till the very last minute gives us enough time for other ideas to come up.
This seems to be a recurring problem in knowledge work where a large effort that has "deadlines" tends to keep being missed. The cause? Not having enough slack or diffused time to just think. Often it's juggling the task ontop of a thousand others and being constantly distracted.