You don't have to win this one
It was Tuesday
You're at dinner, some months on, and your partner says the plumber came on Wednesday. He came on Tuesday. You know he came on Tuesday. The urge arrives, as it always will, and behind it, a second later, the two questions. Is it true? Probably, you took the morning off. Does it matter? It doesn't. Nothing hangs on it. You say "you might be right, it was that sort of week", and ask whether they heard back from the school, and they did, and dinner goes on at the temperature it started at.
The route to their parents' came up on Saturday, and you said "let's try the back road, you know it better", and it was slower, and neither of you mentioned it, and the journey had a conversation in it that the motorway never had. Their mother said something on the phone last week and your partner told you about it, in full, with an impression, and you laughed, and didn't dispute the wording, and they told you the next thing too.
There was a real one, in March. The extension. You asked for Saturday morning and got it, and said what you thought, plainly, with the numbers, and they said what they thought, and neither of you produced a calendar, and the extension is happening in a smaller form than either of you had argued for, and you both think it's right.
Your partner said something in April that you've kept. They said the house had got quieter, and then corrected themselves, and said no, that wasn't it, it had got easier to talk in. They didn't connect it to anything. You did, and didn't say so, which is a kind of drop too.
None of this is a transformation. You won one last month, about the thermostat, and knew it on the sofa, and said so, and they said "it's fine, it was a bit warm", which was a drop from their side, and you noticed that they'd learned the sentence from you. The list is still going, in your phone. The column for who won has stopped meaning anything, because most of the lines say "dropped", and the column for the evening after says the same word down the page, and it's a different word from the one it used to be.
If you take one thing from this book, take this. Next time you reach for the calendar, ask yourself whether it matters, and if it doesn't, say "you might be right" and change the subject. That's the whole method. Everything else is detail.