A while back, I stumbled on an article with some clever advice on getting writing done. Write twelve sentences. That's it. If you want to keep writing past that, do it. If not, then you've got your twelve and you're good to go. No guilt for not churning out 2000 words a day. Just small, consistent forward progress.
I started trying it and oddly enough it worked. I can rough out that much in probably 15-30 minutes. While life has gone crazy, most days I can find at least that much time to sit down and scribble.
What about continuity? What about getting a good writing flow going? Well, those are valid concerns. But I was planning on editing the novel before I shuttle it off for the world to see, right? Right? You think there won't be continuity issues even if I write the whole thing in five page chunks?
And the short bursts don't prevent that writing groove from showing up sometimes anyway. Several times I've sat down intent to just get my twelve in, and instead ended up writing pages. If I'd thought about it beforehand, I probably wouldn't have started--too much to do, floors to clean for our crawling daughter, dishes to put away, laundry to run. But the easy-in of writing just twelve sentences got my butt in the chair and it took off from there.
I so wish I could find the original link that started this off for me, but there's a book with 'twelve' and 'sentence' in the title that totally obscured my hopes of finding it. Cory Doctorow wrote something very similar not long after, though--he says a page, but it works out to the same idea.
Slow and steady beats waiting for uninteruptted time hands down.