Hit pause on the comeback. Clever lines said in anger usually cost more than they win.

The sharpest thing you could say tends to arrive exactly when saying it is most expensive. Anger makes wit available and judgement scarce, so the line that wins the exchange is also the line the other person will still be able to quote in a year. The satisfaction lasts about ten seconds and the repair takes considerably longer.

When the perfect comeback appears, hold it and say nothing. Write it somewhere private if you need it out of your head. Return to the actual disagreement once you can make the point without the sting attached.