How Do You Know When a System Has Failed?

Favourite idea/metaphor from this one:

"We are like sailors who on the open sea must reconstruct their ship but are never able to start afresh from the bottom…The ship needs to be repaired, adjusted, and remade, but this must be done while it sails.”

https://www.newyorker.com/culture/open-questions/how-do-you-know-when-a-system-has-failed?