"I know exactly what it's about, they just won't admit it"

If chapter 11 landed, you may have had a fast reaction to it, which is that you've known for years what's underneath, and the problem is that your partner won't accept it. You feel left to it. That's the underneath. Case closed, and the row is now about getting them to see that.

Sanford's two worries weren't offered as a choice between the two of you, and he measured them one person at a time. But I'd put an interpretation on his finding, and I'll be clear that it's mine. In most one rows, the two of you aren't in the same worry. One of you is in left to it, and the other is in blamed. The pusher from chapter 8 is usually the one who feels left to it, and the quiet one is usually the one who feels blamed, and each one's worry is produced by the other's behaviour. You feel left to it, so you push. They feel blamed, so they go quiet. Their quiet is what leaves you to it. Your push is what blames them. It's one row, seen from two sides, and each side's underneath is real.

Which is why "I know what it's about" gets nowhere. You know what it's about for you. They know what it's about for them. And each of you is trying to get the other to admit to an underneath that isn't theirs. When you say "you leave me to do everything", they hear "you're being blamed", which is their worry, and they defend, and when they defend, you hear "I'm on my own with this", which is yours. Both of you are right about your own underneath and wrong about the row, because the row has two.

The earlier book It wasn't about you is about assuming someone's remark was aimed at you when it came from their day. This is a cousin of that. Your partner's quiet isn't aimed at you. It's what someone does when they feel blamed. Your push isn't aimed at them. It's what someone does when they feel left to it. Once you can see the other person's worry as a worry rather than as an attack, the instance has somewhere to go that isn't the record.

Chapter 21 will ask you to agree what the row is about, and the agreement has two halves, one each. Not one underneath that the other has to admit to. Two, said side by side, without deciding which is the real one. That's a shorter and stranger conversation than the one you've been trying to have, and it's the one that works.