There's an interesting short short story (under 1000 words) contest going on. The deadline is March 16, 2007, and you'll find details at bebo.com.
The contest promotes the publication of a book of short stories, "Nanotales," written by Ziv Navoth. On the site he describes how he overcame a crippling inner critic by taking part in an improvisation class taught by Keith Johnstone, author of the wonderful book, "Impro." (By the way, if you need to overcome a harsh inner critic, you'll find a downloadable trance for that purpose on my website, www.timetowrite.com.)
He then committed to writing one short story a day and made sure he stuck to his plan by asking a friend to monitor his actions. You can adapt this excellent strategy to your situation: your promise could be 250 words a day of your novel or memoir, or 1000 words a week, or whatever you find challenging but doable.
ps: When you get to the Bebo page about the contest, it triggers a video of Ziv Navoth talking about writing stories. But it's down the page, so you may wonder at first who's talking and where it's coming from.