Rehearsing comebacks in the shower means the conversation isn’t over for you. Have it or let it go.

The replaying is a signal, not a hobby. Your mind keeps staging the scene because something in it is unfinished, and the imagined version lets you win without any of the risk of actually speaking. Meanwhile the real conversation stays exactly where you left it, and the energy goes nowhere.

Pick one of the two doors. Either say the thing to the person in plain words, badly if necessary, or decide out loud to yourself that you are done with it. Only one of them fixes anything, and you get to choose which you need.