Ask HN: How do you determine if something is a sunken cost VS needing patience?

I think most of us heard about something called the sunken cost fallacy.

It implies that someone might keep investing in an endeavour because they have already invested a lot up to this point instead of investing their energy in something else which would be more beneficial for them.

However, in practice, I find it very hard to determine when to give up and switch to something else VS be patient to obtain the best result.

I wonder what HN thinks on the topic.