Academic writing is similar. Due to teaching and admin (and other research) commitments, you rarely have the luxury of a full day free to do nothing but write. So doing it little and often is really the only way forward. This then brings us back to the Seinfeld story: how can we make sure to fit the writing in, and not forget about it?
The trick is to introduce some secondary motivation, which is stronger than the motivation required for simply writing something. In this case you get a big calendar, and every day you do your writing, you mark this on the calendar. After a few days you start getting a 'chain' of marks on the calendar, and your mission is to keep the chain uninterrupted. Now the issue is no longer to 'write something', but more like 'don't let the long chain break', and it becomes more and more important the longer the chain is.
You need a clearly defined goal, so that you can be sure when you've done your daily deed. I set it to at least 200 words; in a week this would give me 1000 words, and roughly 50,000 words in a whole year. Obviously I won't stop if I can write more than 200, but that is the minimum. I need to think about how to deal with post-editing, when I basically cut out words, so that should probably be as a period of time, eg half an hour or so.
The next step is to tell everybody. It's a lot harder to break the chain if people who bump into you on the corridor ask how many links you've got. And it might give them ideas about trying it themselves!
I started on Monday, and managed to keep up the chain for the whole week (I only count weekdays, not the week-end). In the process I have produced about 5000 words (not including any blog posts); now where did that time come from? The answer is, I'm more focused on my work. Those little periods 'between things' are suddenly no longer wasted, because I always have 'MUST WRITE' at the front of my thoughts. Just because I don't want to have to tell anybody that I broke the chain.