Measuring the cycle, not the weight
The scales have been the measure of the cycle, and they're the wrong instrument, because they measure the thing the cycle can't deliver and they ignore the thing it can.
Count fresh starts. The measure that matters is how many diets you've started this month. Last year that number was probably one or two a month. The goal is zero, and it's a goal you control completely, which the number on the scales never was. Put a mark on the envelope for each fresh start you don't have, if that helps, or simply notice that the envelope has stopped growing.
Scales, if at all, once a fortnight. Weight moves by a couple of pounds a day for reasons that have nothing to do with fat, water, salt, the time of the month, what's in your gut. A daily weigh-in is a daily verdict drawn from noise, and it's been part of the cycle, because a bad number on Thursday morning is a reason for the biscuit at half past three to become a write-off. If you want to know your weight, once a fortnight is enough to see a trend, and never is a respectable choice.
Other measures. How many meals this week did you eat as meals, sitting down, without a rule and without a feeling? How many days did food take up less of your thinking? How many biscuits were biscuits? Did you eat breakfast the morning after the big weekend? Those are the measures of whether the cycle has stopped, and they're all things you can see without an instrument.
The Sunday night count. The other measure worth keeping for a month is how many Sunday nights had a plan in them. Not whether you acted on it, but whether the feeling came, the urge to download something and start tomorrow. It'll come for a while. Counting it turns it from a temptation into a symptom, and a symptom you're counting is one you're watching rather than obeying.
Clothes, if you want a slow measure. A pair of trousers that fit tells you more than the scales do, over months rather than mornings, and it can't be read at six in the morning as a verdict on the day ahead. If you need to know something about your size, let the trousers tell you, once a season.
The list stops growing. The envelope from chapter 1 is your record. If it has no new entry for three months, the habit this book is about has stopped, whatever the scales say. That's the success this book is aiming at, and it's the one the fresh start never offered.