When to allow yourself to quit, or when you can quit without being labeled a quitter by people who matter to you? Either way, I don’t think the answer lies with me or my peers on the internet.

My opinion you’re in the right track in thinking about objective criteria level of effort, results) and timelines. I also agree that being honest with yourself about the effort bit is super important - building a unicorn can’t be done in half measures.

Edit: Typo.