"I'll do it every day"

The other thing the wish tends to be is daily. Every day, from the first. And for the good fortnight, every day it is, and then a day gets missed and something odd happens in your head. The missed day feels like the end of it. The streak was the thing, and the streak is gone.

Phillippa Lally, Cornelia van Jaarsveld, Henry Potts and Jane Wardle followed 96 volunteers who'd each chosen a new daily behaviour, eating, drinking or activity, done in the same context each day, and asked them to record how automatic it felt. Automaticity rose over weeks on a curve that flattened out, and the time to reach the plateau ranged from 18 days to 254. And missing a single opportunity didn't materially affect the process. The habit went on forming.

Two things follow for January. The first is that the wish is usually set on the assumption that a fortnight is enough to make the thing stick, and it isn't, not for most people and not for most behaviours. The good fortnight is a fraction of the way along Lally's curve. If you drop at three weeks, you've dropped at a point where the behaviour was always going to feel like effort, because that's what it feels like at three weeks. It's not a sign it wasn't taking. It's what taking feels like early on.

The second is about the missed day. Lally's data say a single miss doesn't undo formation, which means the feeling that the streak was the thing is wrong in the specific way that matters. The streak is a picture. It's a clean row of ticks, and it's pleasant in the way the picture in chapter 5 is pleasant. The habit isn't the streak. The habit is the tendency to do the thing on the next ordinary day, and that tendency was still there the morning after the miss. What ended it was your reading of the miss, not the miss.

This is why the Tuesday sentence in chapter 18 isn't daily unless the thing genuinely needs to be. Three days a week with a plan survives a missed Tuesday, because Thursday's still there. Every day with no plan breaks the first time life is larger than the wish, and it always is, some day in the third week.