"A bad day needs one"

It does. A day that went badly should end with something good in it, and I'd say that to anyone. The problem is what happens to the bad day when every day gets the same thing.

Picture the week. Monday was ordinary and got a glass. Tuesday was the worst day in a month and got a glass. Wednesday was fine and got a glass. The bad day and the ordinary day ended identically, which means the bad day got nothing extra. The thing that was supposed to be there for the hard days was already spent on the easy ones, and on the hard day it's just the routine, the same glass at the same hour, marking nothing. An earlier book in this series, Cook the simple thing, makes a version of this point about takeaways, and I won't repeat it. The angle I want is from the other side, from the bad day itself.

A bad day needs something that recognises it was bad. That's the need. The daily can't recognise anything, because it's the same on every day. So on the bad day you do one of two things. You have the daily, and it does nothing, because it's what you'd have had anyway, and the bad day goes unmarked. Or you have more of it, a second glass, a bigger order, three episodes, and the more is the marker, which means the marker for a hard day is now excess, and excess is what you'll reach for every time a day feels hard.

The daily can't scale. That's the whole difficulty. It's set at a level that fits an ordinary day, and an ordinary day is most days, so there's nothing left to do on the day that isn't ordinary except go past the level. And if the daily is alcohol, going past the level on the hard days is exactly the pattern the NHS pages describe as the one to watch.

Here's the alternative, and chapter 20 fills it in. If the treat isn't daily, a bad day can have one and the treat does its job. It says this day was different, because most days don't get this. The same glass, on a Tuesday that was awful, after a week of evenings without it, is a marker. It recognises the day. The daily can't, because it's already been used on Monday.