Similar to writer's block, a writer is mentally incapacitated from writing. However, the incapacitation stems from lack of willpower or lack of interest/enthusiasm in the actual project, rather than a lack of imagination or creativity. Is often paired with, though not necessarily a part of, procrastination. Can be used as a verb (i.e., writer's balking, writer's balked).
1: Hey, did you start that essay that 3 assigned you?
2: No. Writer's balk. It's a shitty subject to talk about. I don't like writing about it.
3: What's keeping 5 from finishing the review?
4: She writer's balked because the movie is that awful.
3: Do I have to finish it?