"I'd never do that"

The charge survives because of a comparison you don't notice making. They didn't reply for two days, and you think, I'd never leave someone hanging like that. They forgot the date, and you think, I don't forget. So the act must come from something in them that isn't in you.

Now look at your own week. There's a message you haven't answered. There's one you answered a week late with "sorry, this got buried". There's an email you sent with no greeting because you were writing four at once. There was a time you interrupted someone, probably today, and you didn't notice it as an interruption because from the inside it felt like joining in. There was a birthday you remembered at nine in the evening. There was a roundabout. If you've done every kind of slip in this book, and I'd put money on it, then you know exactly what a slip usually means, because you know what yours meant. They meant you were busy, tired, distracted, and thinking about something else. They meant nothing about the other person at all.

The old idea was that people explain their own behaviour by circumstances and everyone else's by character, across the board. Bertram Malle went through 173 published studies in 2006 and found it wasn't that simple. Across everything, the asymmetry barely existed. But it did hold for negative events. When something bad has happened, people explain their own version by the situation and other people's by the person. For good events, it reversed. So the lean isn't a general failure to see other people's circumstances. It's a specific lean that appears exactly when someone has done something you didn't like. Which is when the charge gets made.

So the comparison "I'd never do that" is false twice. You would do it, and you have, this week. And the reason you don't count your own version is that the thing that makes you generous to yourself, knowing the circumstances, is the thing you're not bothering to imagine for them. Your own week is the base rate for what slips mean. Use it.