"I can't leave until it feels right"

Some readers will recognise a different criterion. It's not that they're weighing risks. It's that they can't leave until something inside says done. They push the handle and wait for the feeling. Sometimes it comes on the first push. Sometimes it takes four. The checking stops when the feeling arrives, and not before.

I want to look at that feeling, because it's doing a job it can't do. What follows is my own reasoning, on top of the research above.

The feeling of certainty is not a measurement of the door. It's a state in you, and it depends on things that have nothing to do with locks. You're tired. You're late. You had a row last night. There's a difficult meeting at ten. On those mornings the feeling is slow to come, and the door gets checked four times, and the door was exactly as locked as on the morning it came at once. If the feeling were tracking the lock, it would be the same every day, because the lock is.

Worse, the feeling is being worn down by the checking that's meant to summon it. Chapter 3's finding is that each recheck fades the picture, and a faded picture is precisely what "doesn't feel right" is made of. So you're waiting for a sense of clarity while doing the one thing that removes clarity. On a bad morning that's a loop that can run until you're late, and the eventual leaving is exhaustion, not certainty.

The way out is to change what decides. Not the feeling. The check. You did the once. You saw the door lock, you heard it, you said so. That's the evidence, and it was complete at the moment it happened. Whether it feels right afterwards is a fact about your morning, and you can note it and leave anyway. The doubt is allowed to come with you in the car. It isn't allowed to turn the car round.

That sounds cold, and for the first week it will feel like walking away from an unlocked house. It isn't. The house is locked. What you're walking away from is a feeling, and chapter 18 is about how to do that without it being unbearable. What I'd ask you to notice for now is that the feeling of certainty was never reliable, and that you've been letting it decide anyway. Deciding by the check, done once and well, is more careful, not less.