Quarrels would not last long if the fault was only on one side.

A dispute that keeps going is being fed from both ends. The original wrong may well have been one person’s, but the continuation needs two: someone to keep replying, keep remembering, keep declining the half-offer. That is not a way of saying the injury was not real or that blame is always even. It is a narrower point about duration, which is a separate matter from cause.

In the argument that has outlived its subject, look only at your own contribution to the length of it. Find the smallest thing you could stop doing, stop it without announcing it, and see whether the quarrel has enough fuel left to continue.