Writer's block
A lasting inability to write despite the desire to — a symptom with many causes rather than a single ailment.
Writer's block names the persistent inability to produce text despite the intention to write. The commonest error is treating it as a single entity: it's a symptom, and the remedy depends on the diagnosis. Perfectionism is treated by writing badly on purpose (first draft, freewriting); a story problem (the scene refuses because the plot broke upstream) is treated by re-planning; exhaustion is treated by resting — not by forcing; fear of judgment is treated by lowering the stakes.
Two transversal levers enjoy consensus: shrinking the unit of work (one scene, 200 words, ten minutes — inertia yields to small doors) and radically separating production from evaluation, since block is almost always born of their collision.
Example
Stuck on chapter 12 for three weeks? The problem is often back in chapter 9.