Go to bed cross if you have to
Call the truce
The next three chapters are the method. This one is the sentence that stops the sofa, and it has to be agreed before the night it's needed, because at eleven nobody's agreeing to anything.
Agree it on a good day. Not during a row. On a Sunday, with tea, the two of you decide that after ten o'clock, either of you can call a truce, and a truce means the row stops and a time gets named. Say it out loud to each other and mean it. This is the part of the method that's done once and makes the rest possible.
The sentence. "I care about this too much to do it tired. Eight o'clock." Or your own version, as long as it has three things in it. That the row matters. That the hour is wrong. And a time. Practise it on the Sunday. It'll feel absurd and it'll be there at eleven when nothing else is.
Either of you can call it. This is what makes it a truce and not a withdrawal. It isn't the property of the one who wants to stop. It's a joint rule that either of you can invoke, and when it's invoked, the other one honours it, because that was the agreement on the Sunday.
No last word. The truce is called and the row stops there. Not after one more point. Not after "and another thing". The person who calls it doesn't get to call it and then say the thing they wanted to say. The person who receives it doesn't get to answer. The row stops mid-sentence if that's where it is, and the sentence goes on the note for the morning.
It isn't a win. Calling a truce isn't winning, and neither is receiving one. Nothing has been conceded and nothing has been settled. The score, if either of you keeps one, is unchanged. That needs saying on the Sunday too.
Expect it to be refused at first. If the old rule has run for years, the first truce will be met with "no, we're sorting this". The answer is the sentence again, and then standing up. It's not a negotiation. It's the rule the two of you made, invoked, and the person refusing it will be the person keeping the appointment at eight, and that's when they'll see what it's for.