Kafka isn't simply saying writers must write—he's identifying a peculiar form of self-betrayal where the creative impulse becomes trapped, festering from disuse like an untreated wound. The word "monster" is brutal because it suggests the writer doesn't merely suffer in silence; the blocked impulse deforms them into something unrecognizable to themselves. We see this plainly in people who've abandoned creative work not from lack of talent but from fear or practicality—they often develop a curious bitterness, as though some vital part of their nature has curdled. Kafka knew that for certain temperaments, writing isn't a luxury you can shelf; it's the mechanism by which you remain human.