The decision

You've got the argument and the method. What's left is to decide, and I'd like the decision to fit in one sentence.

If it's under a mile, I walk. If it's under three floors, I take the stairs. Unless I've got a reason I'd say out loud.

Three parts.

The first is the line. A mile, three floors, drawn on a map, with the top five regulars timed both ways. Fixed for a fortnight.

The second is the arrangements. Keys with a step in them, shoes by the door, the bag on the peg, the far end of the car park, two school runs on foot.

The third is the reason. Written down in advance, said out loud when used, and used honestly. The big shop is a reason. The keys being in your hand is not.

There's a form of planning that helps with rules like this, and it's been tested many times. Peter Gollwitzer and Paschal Sheeran reviewed ninety-four studies of it in 2006. You decide in advance what you'll do and when, in the form "when this happens, I'll do that", and people who plan that way follow through much more often than people who only hold the intention. So write three.

When I need something from the shop, I'll put the shoes on and take the bag.

When I'm in the lift lobby and it's under three floors, I'll go through the door to the stairs.

When I'm driving somewhere outside the line, I'll take the first space I see and walk from it.

What to expect. This is my expectation and not a finding. The first few days you'll find the keys in your hand before you've thought, because the default is fast, and you'll put them back in the drawer with a small feeling of foolishness. That passes. By the end of the first week the shoes by the door will have started doing their work and two or three of the top five will have gone on foot. You'll have timed at least one and been surprised. Around the second week the stairs will have stopped being a decision, because the stairs are the easiest part of this and the body learns them fastest. Somewhere in the first month you'll walk to the shop in the rain in a coat and find it was fine, and that's the day the weather objection ends. The step count, if you're keeping one, will be a couple of thousand higher than it was on the same working day a month before, without anything you'd call exercise having happened. And you'll notice, on the walk home from something, that you're thinking about a thing you've been stuck on, and that it's moving.