Don't try to salvage what's rotten
Sometimes some things end.
But we refuse to accept it and try to salvage it.
First, it's important to realize if something has lived its course and is rotten. Second, when that is the case, it's not only necessary but also easier to just start over or move on.
Sure, maybe after tons of hard work and time invested you could maybe turn it around. Maybe. But that's never guaranteed.
It's simpler and easier to start over.
The time you'd spend trying to salvage a rotten thing has an opportunity cost to it. You could instead use that time to begin the new thing and get better results than messing with the old thing.
Relationships are a good example of this.
If it's broken, just scrap it and start from 0. It's hard because of all the investment, but sometimes you have to cut your losses and stop wasting your time and resources.