Winston Churchill’s “never give in, never, never, never, never” is an oft-quoted trope. The end of the sentence is always left out: “except to convictions of honor and good sense.”
But giving up is, in my opinion, a critical part of adulthood. Pyrrhic victories are a lot worse than graceful surrender, and a negotiated truce with your task list is a hell of a lot more effective than burning out.