I had a saying as an undergrad: “As time to the deadline goes to zero, my productivity goes to infinity”. This is how I lived back then. There’s a good chance that I didn’t start any homeworks or projects until the night before they were due. Not one. On more than one occasion, I was finishing papers within minutes of when they were due. But everything got done on time and I got really good grades.

So why start early? I succeeded pretty well as an 18-22 year old by starting at the last minute. Well, three main reasons.
One: It’s stressful to work against the deadline all the time.
Two: I didn’t do my best work. This didn’t matter much in undergrad courses, but does matter for most things in life.
Three: It’s hard to work and live with other human beings and procrastinate all the time. In undergrad, I largely worked and lived independently. Now, I have bigger projects with more people involved. And I live with my fiancée, Maria. And it’s not fair to all these people to be selfish with my time and start at the last minute.

I still procrastinate, but I’m light-years ahead of where I was a half-decade ago.

The trick, besides starting early, is avoiding “acceptable inefficiency” when not working against the deadline. Without a deadline to motivate myself, I find myself working less efficiently than I could be. This inefficiency seems acceptable because no noticeable problems arise. But by spending more-than-necessary time on a project, the unseen problem of less available time arises. Less time for other projects, less time for leisure. So start early, but don’t let the lack of deadlines hurt that peak efficiency you used to have when you battled deadlines.

(image from http://www.pausecutplay.com/blog/2013/4/14/dont-fucking-procrastinate-rules-of-a-creators-life.html)