"I'll just be extra nice to make up for it"

There's a response to the reading that looks like kindness and isn't quite. Once you've concluded that the mood is about you, you set about repairing it. You're warmer than usual at dinner. You make the tea. You apologise for the bins, or for the plan, or for nothing in particular. You send a follow-up email to the manager with more detail than anyone asked for. The evening becomes a campaign to put right a thing that, on the evidence of this book, mostly didn't happen.

Look at it from the other side of the table. Your partner came home tired and quiet. Now the person opposite them is being unusually attentive, apologising for things they don't remember, watching their face for signs of thaw. From the inside of a bad day, that's confusing, and it asks something. It asks them to respond to a repair for an offence they haven't registered, and the easiest way to respond is to reassure, and now the tired person is doing the reassurance job from chapter 18 at the end of a day that already took everything.

The repair also confirms nothing. If your partner softens over the evening, the reading says the repair worked, when what happened was that the bad day wore off, as bad days do, on their own clock. If they don't soften, the reading says the offence was worse than you thought. Either way the reading comes out of the evening stronger, and you come out of it having spent the evening managing a mood that was never yours to manage.

There's a version of this that's an apology for nothing, and it's common enough to have a book of its own later in this series. Here I'd only say that "sorry" for a thing you didn't do teaches the people around you that your apologies are a way of checking the weather rather than a response to a fault, and that's a costly thing to teach them, because the apologies you mean will be heard the same way.

The alternative is the check. "Rough day?" does in one sentence what the campaign does in an evening, and it does it by asking about them rather than by managing them. If the answer is that it was about you, chapter 24 is about what to do, and it's a conversation about a thing and not a campaign of warmth. If it wasn't, the repair was never needed, and the evening is yours.