As I "said recently":http://chadfowler.com/2008/12/4/develop-a-good-habit-in-20-days, 20 days is the right length for me to develop beneficial habits. It just so happens that, counting today, there are 20 days left in 2008.
So what should we do? I'm thinking about trying to write fiction every day for the rest of the year. Or practice the saxophone. Or write short pieces of "classical" music. I'm not sure yet, but I have the rest of the day to decide and put the plan into action.
My friend "Erik Kastner":http://metaatem.net/ showed me recently that Steve Pavlina posted something "similar":http://www.stevepavlina.com/blog/2005/04/30-days-to-success/ a few years ago. At the bottom of the article he includes a bunch of ideas of things you could try to do for 30 days. So if you're interested but don't know what you want to do yet, have a look at his suggestions. They might trigger an inspiration.
Update: I chose fiction writing. Time will tell.