I think deadlines are a sufficient condition for procrastination but not a necessary one. And even starting a project earlier is no guarantee of avoiding a last minute crunch. (When I was studying I’d start projects on time, get the “hard parts” done, but still end up finishing them off at the last minute. Whether that’s a function of anchoring or just plain vanilla Planning Fallacy, I’m not sure).
Without a deadline, can you still procrastinate? Of course, but the consequences of not starting are less immediate, but still
potentially severe. If you don’t finish writing an essay by the deadline, you fail a course. If you don’t submit an application, nothing happens now, but restrict your options later. If you never exercise, you’re more likely to get sick as you age.
So having decided to start, how do you maintain momentum? From a comment above, breaking down a single project into sub tasks with their own deadlines is a great start. But there’s still a trap here—the comforting thought that some sub tasks will take less time than others, and you’ve got heaps of time to the actual deadline to catch up. Quantifying what you’ll achieve (e.g. I will write the introduction and conclusion by the end of the week) provides a concrete goal and also harder to lie to yourself about how much time you have.