Tackling multiple writing objects simultaneously

Graham Harman, a prolific writer, gives advice on writing. He writes that he could write a 120-page manuscript on a cross-country bus trip. That's amazing, but I'm not sure how he can do that. And right now, he has to finish 6 papers by January 31. The main points seem to be to just get started, even if it's only a page or two, and to have several projects going on at the same time:

That’s why you need to get away from the “lonely desert monolith” conception of projects. You should have several of them simultaneously, like an ecosystem of projects. When you’re sick of one, you can turn to one of the others.

If you get in that habit, you’ll soon find yourself doing a lot every year. Do that over the course of several decades, and you’ll have had an extremely productive career.