"I'd let it go if they'd just admit it"
Every instance of the one row carries the record with it. Not just the thing from March, though that's usually in there, but the whole shape of the past, how it's always you who asks, how they've said they'd change and haven't, how last time they promised. The record feels like evidence. It feels like the thing you're being reasonable about, and the reason you can't let tonight go is that letting tonight go means letting the record go, and the record is what you've got.
Bradbury and Fincham, reviewing the research on how married people explain each other's behaviour, found a consistent pattern. Dissatisfied spouses explained their partner's behaviour in ways that cast it in a negative light, and satisfied spouses didn't, and there was evidence that the explanations weren't just a symptom of dissatisfaction but helped cause it. Their word for these explanations is attributions, and the plain version is this. The same full dishwasher can be read as "they forgot" or as "they don't think it's their job", and which reading you make isn't decided by the dishwasher. It's decided by the record, and the record is made of earlier readings.
That's what I'd ask you to notice about the record. It's not a file of facts. It's a file of readings, each of which was made in the middle of an instance, at the angriest moment, in the version of your partner you see when the row is on. Sunday's "they said they'd do it and didn't" was a reading. March was a reading. Some of the readings are fair. But the file was compiled by a witness who was upset every time, and it's being consulted as though it were a record of what happened.
There's another thing about the record. Your partner has one too, and theirs has you in it, with the same fairness and the same problems, and when you open yours they open theirs, and now there are two files on the table and no dishwasher. If you find yourselves keeping a running count of who did what around the house, that's a habit of its own, and it's fed from the same file.
The earlier book You don't have to win this one is about the argument over who's right about a fact. If your instance is that, go there. And if you've noticed, in the middle of an instance, that you've stopped believing the point you're defending, You can be wrong out loud is about the next five words. This chapter is only about the record, and what it asks is small. The next time the one row starts and you reach for March, notice that you're reaching for a reading, and put it back. Chapter 22 will say the record stays shut. Here I only want you to see what it's made of.