"Going to bed cross means we've failed"

The old rule has a second layer, and it's about what going to bed cross says about the marriage. Couples who are all right don't need to. The fact that you'd have to means something's wrong.

Look at what the settlement at one in the morning actually is, in the cases where you've reached it. One of you gave in. Or one of you cried and the other stopped. Or you both said fine and went up. Those aren't settlements. They're endings, produced by exhaustion, and they've told you nothing about the dishwasher or the thing from March, and they've left the two of you with a memory of the night rather than of a resolution. If that's what not failing looks like, it's a low bar, and it's the bar the old rule sets.

A truce isn't failure. It's two adults recognising that the hour is wrong for the conversation and agreeing to have it at a better one. That's a more competent act than anything that happens at one in the morning, and it's the act of a couple who can manage their disagreements rather than be managed by them. The couple who can say "we're both too tired for this, eight o'clock" and go up cross and be at the table at eight are doing something harder and better than the couple who stay on the sofa till one because a rule told them to.

Cross is a state. It isn't a verdict on the marriage. Two people who love each other can be cross with each other on a Tuesday night, and sleep, and be less cross at eight, and sort the thing, and that's what a marriage with disagreements in it looks like from inside. The old rule has made cross into a thing that has to be resolved before sleep, and resolved-before-sleep has become the test of whether you're all right, and the test is producing the sofa at one, which is the thing that's actually not all right.

You haven't failed if you go to bed cross. You've declined to fail at one in the morning so that you can succeed at eight.