The decision

Here's what I'd suggest, and it's one rule with three versions, chosen once and held for four weeks.

The rule. One reading or none, written down, read as part of a column and never on its own. In the weigh day version, that's one reading a week. In the average version, it's a daily reading you don't look at and a weekly figure you do. In the break version, it's none for a month.

Choose now, before the next morning, because the next morning is when the habit will make the choice for you. Chapter 17 said which suits whom. If you're in doubt, take the break.

Then three plans in the form the research calls implementation intentions, which Peter Gollwitzer and Paschal Sheeran found, across a large body of studies, to make a decided action much more likely to happen. The form is when this, then that, with the this being a specific moment and the that being a specific act.

When I walk into the bathroom in the morning, then I do the thing I've chosen. For the break, that's walk past where the scale was and put the kettle on. For the weigh day, on the six other mornings it's the same, and on the day it's one step, one number in the notebook, off. For the average, it's step on, write the number without reading it, off.

When the number swings me, then I look at the column and not the scale. If there are fewer than four entries, I say not enough points. If there are four or more, I read the direction, not today.

When my hand goes to the mat on a day it shouldn't, then I say the words out loud, or as good as. That's water. And I go and do the next thing. The words aren't a spell. They're a reminder of chapter 3 at the moment chapter 3 is most likely to be forgotten.

What to expect. Phillippa Lally and colleagues followed 96 volunteers learning a new daily habit and found that it took, on average, a couple of months to become automatic, with a wide range, and that missing a single day made no material difference to how the habit formed. The habit here is partly a not-doing, which is different, but I'd expect the same shape. The first week is effort, the second is less, and somewhere in the second month the bathroom is just a bathroom. And one morning back on the scale, chapter 24, doesn't undo it.

What you don't do. You don't announce it, unless there's someone in the house who weighs too, in which case chapter 22 has a word. You don't replace it with a daily anything, chapter 20. And you don't, on any version, take a second step.

That's the decision. It's small, it's specific, it takes a month, and at the end of the month you'll know something about your mornings that you can't know any other way.