Put a number on regret and it becomes a target; put a target on it and the number stops meaning what it meant. The usual story is that we are careless calculators. The better story is that we are careful about the wrong things. The lesson is modest. Build for the person who exists, not the one in the model. Understanding people turns out to be a more urgent task than changing them, and a great deal harder.
What it gets right
Every one of us runs the same shortcut, and every one of us believes we are the exception. The point is not that people are foolish. The point is that regret is expensive, and we economise on it like everything else. The lesson is modest. Build for the person who exists, not the one in the model. The strange thing about the last biscuit is not that it exists but that it works, most of the time, for most people.
