"We've always argued like this, it's fine"

Some couples will say this is just how they are. They bicker. It's been twenty years. Nobody's hurt.

Two things. The first is the score. If you kept the list from chapter 1, look at the column for who won. If it's mostly you, that's not two people bickering. That's one person winning and the other one conceding, twenty years running, and I'd ask what the concessions have been made of. Some will have been real agreement. Most, in my experience of people who look at this honestly, are "whatever", which is a way of leaving the argument that leaves the fact with you and the feeling with them.

The second is a pattern that researchers have studied in couples for decades. Andrew Christensen and Christopher Heavey, in 1990, filmed thirty-one couples in two disagreements each, and described what they called the demand and withdraw pattern. One partner presses, with requests and complaints and criticism, and the other retreats, with defensiveness or silence. They found that both partners were more likely to press when discussing a change they wanted, and more likely to withdraw when discussing one the other wanted, and that men withdrew more overall. It's a small study and it's about wanted changes rather than plumbers, and I'd hold the gender finding loosely. But the structure is the thing to notice. When one person presses, the other withdraws, and withdrawal isn't agreement. It's a way of ending the exchange without conceding the point, and it leaves the point unresolved and the presser feeling they've won.

Kennedy and Pronin's spiral from chapter 4 tells you what twenty years of that does. Each of you has a settled view of the other as the difficult one. Each of you has twenty years of evidence for it, gathered from inside the spiral. The bickering isn't fine. It's a stable arrangement in which one person is right and the other is quiet, and the quiet one has been keeping the score you haven't, and the score is not in your favour, whatever the calendar said.

If it's really fine, the test is chapter 15's. Do you both enjoy it? Is the evening after the argument the same as the evening before? If yes, you're one of the couples for whom it's play, and this book isn't about you. If the honest answer is that the arguments end with one person on their phone in another room, it isn't play, however long it's gone on.