"I can't sleep next to someone who's angry with me"

The truce is accepted in principle and then the question arrives. Where do you sleep? Lying in the same bed as a person who's furious with you feels impossible, and one of you ends up on the sofa, and now the truce is a separation.

The same bed. That's this book's position, and I'll say why, and chapter 24 covers the households where it isn't the right answer.

A truce called by two people is a truce on both sides. You're both cross. You've both agreed to stop. Neither of you has won or lost. Lying in the same bed cross is the physical form of that agreement, and it says, without anyone speaking, that cross is a state the two of you can be in together, which is true, and which the old rule has spent years denying. The sofa says something else. It says the argument has become a division, and the division is the thing you'd been trying to avoid by staying up.

There's a practical point too. A person on the sofa is a person alone with the row, and alone with the row at one in the morning is the earlier book's three o'clock mind, running the circuit on its own without even the other person to interrupt it. The same bed, with the other person breathing beside you, is a smaller room for the row to grow in, and it grows less.

What lying cross next to someone teaches, over a month, is that it's survivable. The first night it feels intolerable, and you lie rigid, and you sleep anyway, because you're tired and the row isn't live. The third night it's uncomfortable. By the second week it's a thing you've done and know how to do, and the knowledge changes what a row is. A row is no longer a thing that has to be resolved before you can be in the same room. It's a disagreement that two people who share a bed are having, and will finish in the morning, and that's a different and better thing for a row to be.

Say nothing much. "We're not finished and that's fine. Eight o'clock." Then lie down. If a hand finds a hand in the night, that's not the settlement and it doesn't mean the argument's over. It means you're still the two of you, cross, and that was always allowed.