Fatigue can make quitting look like clarity.

Tiredness produces a very convincing kind of certainty. Suddenly the answer is obvious, the project is pointless, the relationship is over, and the clarity feels like insight rather than depletion. What is actually happening is that fatigue has removed your tolerance for difficulty and reframed that as a decision. The conclusions are often about the state you are in rather than the thing you are judging.

Make a rule that you do not quit anything on a bad night. Write the case down and revisit it after two good nights of sleep. What survives that test is worth acting on.