After a friendship-ending fight, you feel an impulse to push through the pain to do an exhaustive postmortem of everything you did wrong in that last, fatal argument—you could have phrased that more eloquently, could have anticipated that objection, could have not left so much "surface area" open to that class of rhetorical counterattack, could have been more empathetic on that one point, could have chosen a more-fitting epigraph, could have taken more time to compose your reply and squeeze in another pass's worth of optimizations—as if searching for some combination of variables that would have changed the outcome, some nearby possible world where the two of you are still together.

No solution exists. (Or is findable in polynomial time.) The causal forces that brought you to this juncture are multitudinous and complex. A small change in the initial conditions only corresponds to a small change in the outcome; you can't lift a two-ton weight with ten pounds of force.

Not all friendship problems are like this. Happy endings do exist—to someone else's story in someone else's not-particularly-nearby possible world. Not for you, not here, not now.