When you are working on a story, what inspires you?
But an additional spin on the question is what inspires us to keep going?
When I'm working on a first draft, I set time goals. I want to make steady progress each week toward reaching some version of a completed draft (beginning, middle, and end). I find word count goals frustrating, personally, because cutting words means backward progress, so I always use time. Knowing that I'm reaching the amount of hours designated for that week inspires me to keep working.
Once I've completed a very rough first draft, I set times goals for revision, as well. Each layer of revision has a specific focus (pacing, characterization, etc) and again, I use the idea of completing a certain number of hours a week to get through each pass. It doesn't matter how long it takes, by the way -- I just plan to achieve the number of hours I've dedicated to the project for the week. (It also helps to have a weekly back-up slot as productivity expert Laura Vanderkam advises, in case a day is derailed by unexpected events.)