It's never okay to quit. It's never okay to stop halfway into something and walk away. It's never okay. But that isn't entirely true. Winners sometimes quit.
Winners sometimes walk away.
Well, at least wise ones. And if that's true, then quitters can win. That they, in the sense of the cold, hard word, quit. It isn't like they are abandoning ship, per se, because maybe they are no longer captain. And when this occurs, it is best to just go gentle into that good night.