My students are often asking me, 'What do you think are the most important qualities for a writer?' And one thing I always tells them is that it's helpful to be willing to sit in a space of uncertainty. There are entire years, especially with novels, where you really don't know where the project is going.
I once took a workshop with Jim Shepard, and he has this term, 'rate-of-revelation,' that has come to mean a lot to me: 'the pace at which we're learning crucial emotional information about the stories' central figures.' An ever-increasing rate-of-revelation is good; a stagnant r-of-r is not.