But what is the difference between sunk cost and necessary persistence? Sometimes it's not obvious at all. There are many cases of people who were failing for

But what is the difference between sunk cost and necessary persistence? Sometimes it's not obvious at all. There are many cases of people who were failing for decades but they persisted and then out of nowhere they got their big break. There are also many cases (probably even more of them) where people persisted but went nowhere. It's only sunk cost in hindsight.