Stop every day right after we feel like we can write more. Save the excitement and carry it over to the next day to let momentum kick off tomorrow's work smoothly.
The writer Haruki Murakami loves running. Sometimes he runs faster than usual but stops the running session earlier. His reason is to let the exhilaration he feels at the end of each run carry over to the next day. Therefore, the next day he can feel excited again going running.
He applies the same principle to his writing. Haruki stops every day right at the point after he feels like he can write more. He saves the excitement and carries it over to the next day. By doing so, the next day's work goes surprisingly smoothly.
This reminds me of Weekly I/O #8.1 about improvisational productivity. While Haruki kicks off the work using previously saved excitement as fuel, Daniel Gross kicks off by bundling thinking the work with doing it. Thinking and planning are the fun parts that can generate excitement as the momentum to finish the work.