Getting the last word feels good for thirty seconds. Being right next month feels better.

The last word is a reward paid out immediately, which is why it is so hard to leave on the table. It also settles nothing. Whatever was actually in dispute gets decided later by how things turn out, and the person who spent their energy on the closing line is not usually the one who prepared for that.

When you notice yourself composing the final reply, put the phone down and ask what would make you obviously right in four weeks. Then go do that instead. Letting someone else finish the conversation costs you almost nothing and leaves you free.