thanks to Rob Scott for pointing out this article

There is, however, another simple technique for avoiding procrastination that has been examined experimentally: using deadlines. Ariely and Wertenbroch (2002) found that self-imposed deadlines were effective in improving task performance but, watch out, people aren’t as good at setting their own deadlines as they are at conforming to deadlines set externally. Strangely, when left to their own devices, people seem prone to handicapping themselves with irrational deadlines.

For the full article:

http://www.spring.org.uk/2009/01/how-to-avoid-procrastination-think.php