This process within our brains is a three-step loop. First, there is a cue, a trigger that tells your brain to go into automatic mode and which habit to use. Then there is the routine, which can be physical or mental or emotional. Finally, there is a reward, which helps your brain figure out if this particular loop is worth remembering for the future:

“I made for myself a million dollars on Pepsodent,” Hopkins wrote a few years after the product appeared on shelves. The key, he said, was that he had “learned the right human psychology.” That psychology was grounded in two basic rules: First, find a simple and obvious cue. Second, clearly define the rewards.

Studies of people who have successfully started new exercise routines, for instance, show they are more likely to stick with a workout plan if they choose a specific cue, such as running as soon as they get home from work, and a clear reward, such as a beer or an evening of guilt-free television.2.13 Research on dieting says creating new food habits requires a predetermined cue—such as planning menus in advance—and simple rewards for dieters when they stick to their intentions.

This is how new habits are created: by putting together a cue, a routine, and a reward, and then cultivating a craving that drives the loop.

Anyone can use this basic formula to create habits of her or his own. Want to exercise more? Choose a cue, such as going to the gym as soon as you wake up, and a reward, such as a smoothie after each workout. Then think about that smoothie, or about the endorphin rush you’ll feel. Allow yourself to anticipate the reward. Eventually, that craving will make it easier to push through the gym doors every day.

THE GOLDEN RULE OF HABIT CHANGE You Can’t Extinguish a Bad Habit, You Can Only Change It.

“That’s why signing kids up for piano lessons or sports is so important. It has nothing to do with creating a good musician or a five-year-old soccer star,” said Heatherton. “When you learn to force yourself to practice for an hour or run fifteen laps, you start building self-regulatory strength. A five-year-old who can follow the ball for ten minutes becomes a sixth grader who can start his homework on time.”