Patience vs Reality

At what point does "waiting patiently" turn into "being too stubborn or stupid to let go"?

There are some things in life that would just drag on endlessly if we didn't put an end to them...how do we know what those things are?

Where's the magic point at which the pain of letting something go is less than it would be if things were left to drag on?

Please tell me there's some sort of equation for this