I’ve learned three things from writing marathons:
1. I can trust my basic prose level to sound okay on first draft, without me paying too much attention to it as it flows out. I need to save my concentration for keeping the whole story in mind. Doing paper edits before the marathon helps a lot on thinking about the story’s shape; so do the comments I get from my workshop on the partial. Making notes after those comments and edits, on specifically what I need to include before the novel’s end, also helps a lot. The notes can be lather, rinse, repeat at each stage of the writing process.
2. Breaks are necessary for me, even in a marathon, even if the breaks are only standing up after an hour or so to put away part of a load of laundry. That’s one kind of break. The other is finishing a large section, then taking a think-break and making notes on the next section, so I don’t have to waste time flailing when I sit back down again to write. I can enforce my think-breaks by, for example, trapping myself downstairs waiting for my laundry to finish, with no entertainment but the notebook and pen.
3. I can write a lot in a short period if I need to, but never as much as I wish I could. I have to remind myself not to have wildly unrealistic expectations; it helps to know what I’ve managed to accomplish in the past.