Cue

The cue triggers your brain to initiate a behavior. It is a bit of information that predicts a reward.

Our prehistoric ancestors were paying attention to cues that signaled the location of primary rewards like food, water, and sex.

Today, we spend most of our time learning cues that predict secondary rewards like money and fame, power and status, praise and approval, love and friendship, or a sense of personal satisfaction.

Craving

They are the motivational force behind every habit/ What you crave is not the habit itself but the change in state it delivers. Ex: You are not motivated by brushing your teeth but rather by the feeling of a clean mouth.

Response

The response is the actual habit you perform, which can take the form of a thought or an action. Whether a response occurs depends on how motivated you are and how much friction is associated with the behavior. Your response also depends on your ability. Ex: If you want to dunk a basketball but can’t jump high enough to reach the hoop, well, you’re out of luck.

Reward

The first purpose of rewards is to satisfy your craving. At least for a moment, rewards deliver contentment and relief from craving.

Second, rewards teach us which actions are worth remembering in the future. Your brain is a reward detector. As you go about your life, your sensory nervous system is continuously monitoring which actions satisfy your desires and deliver pleasure.

If a behavior is insufficient in any of the four stages, it will not become a habit.

Eliminate the cue and your habit will never start. Reduce the craving and you won’t experience enough motivation to act. Make the behavior difficult and you won’t be able to do it. And if the reward fails to satisfy your desire, then you’ll have no reason to do it again in the future.

-Atomic Habits, p.47