I once saw Joyce Carol Oates speak at the University of Colorado. She said being a writer is like having a vice permanently clamped on your head. The only way to loosen the vice is to finish writing something.
I have one of those vices. Mine is radioactive. It weakens my brain. So I have a harder time loosening the vice.
Today I reworked yesterday's paragraph and then I wrote three more for a total of 791 new words, all of which suck.
Then I went for a punishing four mile run in the noon heat, during which it occurred to me that I ought to begin the proposal with an entirely different paragraph. When I got home, I scribbled down an outline.
The vice loosened a little.
When I complete this proposal, which I will do, the vice will be completely removed, and I'll feel elated. As Oates said all those years ago, it's just the feeling of a normal head without a vice clamped on it. But for the writer, it's euphoric.