"I'm just being realistic"

Realism sounds like a defence, so let's take it seriously. Being realistic means matching your beliefs to how things usually are. So the question is what slips usually are, and you have the data. It's your own week.

Go back to the list from chapter 4. How many of your slips, this week, were aimed at someone? The message you didn't answer, the email with no hello, the interruption, the thing you forgot. I'd guess none. You didn't do any of them at anyone. That's not one week's oddity. It's what slips are. The realistic estimate of what a given slip means, from the only large sample you have full information on, is that it means someone was busy. A charge of malice is the unrealistic reading. It's the reading that assumes this person, unlike you, spends their day aiming their carelessness.

There's a second problem with "realistic", which is that you never find out when you were wrong. You charged the friend with not caring, and you never asked, and you cooled a little, and the friendship faded, and the fade looked like confirmation. You charged the manager with coldness, and you never checked, and the manager left for another job, and you never learned that they'd thought you were one of the good ones. The charges that were right get remembered because something happened. The charges that were wrong disappear, because nothing did, and there was no moment where the truth arrived. So your sense of your own hit rate is built entirely from the hits. That's not realism. That's a filing system that throws away the misses.

The genuinely realistic position is uncomfortable and it's this. For most slips you'll never know. The message went unanswered for a reason, and the reason is inside someone else's Tuesday, and it's gone. What you can know is the base rate, and the base rate says busy. Believing the base rate isn't being soft. It's what the numbers say, as far as you can see them.