Then one day, we’ll put the reward in the old place, and put in the rat, and, by golloy, the old habit will rememerge right away. habits never really disappear. They’re encoded into the sturctures of our brain, and that’s a huge advantage for us, because it would be awful if we had to relearn how to drive after every vacation. The problem is that your brain can’t tell the difference between bad and good habits, and so if you have a bad one, it’s always lurking there, waiting for the right cues and rewards.

The Golden Rule of Habit Change: You can't extinguish a bad habit, you can only change it.

Rather, to change a habit, you must keep the old cue, and deliver the old reward, but insert a new routine.

There’s something about it that makes other good habits easier.

If you dress a new something in old habits, it’s easier for the public to accept it.

Shampoo doesn’t have to foam, but we add foaming chemicals because people expect it each time they wash their hair. Same thing with laundry detergent. And toothpaste—now every company adds sodium laureth sulfate to make toothpaste foam more. There’s no cleaning benefit, but people feel better when there’s a bunch of suds around their mouth. Once the customer starts expecting that foam, the habit starts growing.

The brain has this amazing ability to find happiness even when the memories of it are gone.