In a hard conversation, decide your one goal before you walk in. Everything else is noise.

Hard conversations drift. You go in to talk about one thing and twenty minutes later you are arguing about something from March, because everything unsaid wants to come out at once and there is suddenly room. A single goal held firmly is what keeps it from turning into a tour of every grievance either of you has.

Settle on the single thing you need from it beforehand, and say that near the beginning. When the conversation pulls somewhere else, you can say that matters and you want to come back to it another time. Then come back to it, so the sentence stays true.