From the website
"It turns out that every habit starts with a psychological pattern called a "habit loop," which is a three-part process. First, there's a cue, or trigger, that tells your brain to go into automatic mode and let a behavior unfold.
"Then there's the routine, which is the behavior itself," Duhigg tells Fresh Air's Terry Gross. "That's what we think about when we think about habits."
"The third step, he says, is the reward: something that your brain likes that helps it remember the "habit loop" in the future."