Anyway, I find that deadlines, and structure in general, are a good way of getting things done. Some people have enough internal focus that they can just plug away and accomplish tasks without someone telling them what to do or when to do it. It's a good state to try for, but let's be honest -- most of us are distractable to one degree or another. Hey, who's on American Idol right now? Are those storm clouds off in the distance? Rick is back from vacation and has pictures. And so on, and so on.
Having a deadline is a great way to mitigate those distractions and buckle down to do work. It doesn't have to be a "real" one, either. Not all structure has to be external; indeed, self-imposed structure is often the best kind. Nobody is making me post three times a week on this blog, but setting that goal for myself has been very useful (for the most part) in actually sticking to posting here on a regular basis.
Nor does the deadline have to be chronological. A volume quota is another good way to ensure continual progress, and is the idea behind 300 Words, a site created by Hugh MacLeod and Erik Proulx to get writers to commit to putting down three hundred words per day in order to stick with writing (as an aside, MacLeod's book Ignore Everybody is a great read and I highly recommend it). It's a cool idea for a site, and I'd probably participate if it wasn't for already being committed to six blog posts a week!
The point is just to have a finish line of some kind, and the exact form it takes isn't necessarily important. Even a little structure goes a long, long way.