You can’t listen and defend at the same time. Pick one, and pick listening first.

Defending uses the same attention that would otherwise be hearing. While you assemble a reply, the rest of what they are saying goes past unread, and you end up answering the first sentence of a longer point. It feels like staying in the conversation, and it is actually leaving it early.

In the next disagreement, hold your reply until they have finished and you have said back what you heard. If the defence still seems necessary after that, it will keep. Most of the time it turns out to be answering something nobody said.