I think none of those blanket statements here work.

Really it's just odds of finding success vs effort / time spent. And whether that's worth it.

Any of the blanket statements could be true depending on what the exact odds are.

There could be near 0% chance of finding success and it would be better idea to rethink and spend time elsewhere, or yes, there's 10% chance of finding success and it's significant enough that trying 20 times is enough.

If we are talking about e.g. finding a house, if you are not finding any it could very well be that your expectations vs budget is unlikely to find anything and you have to reconsider strategy.

Someone could be repeatedly trying to find work, and thinking it's just a matter of time, but really time would be better spent on improving their strategy, resume, or other means.

These statements to me seem like motivational non-sense which misrepresent how real world works or what the patterns really are like. At best they just give someone a false understanding of how the world works, at worst they make someone spend all their time in the wrong direction.