Habit is probably the most powerful tool in your brain’s toolbox. It is driven by a golf-ball-sized lump of tissue called the basal ganglia at the base of the cerebrum. It is so deep-seated and instinctual that we are not conscious of it, though it controls our actions.

If you do just about anything frequently enough over time, you will form a habit that will control you. Good habits are those that get you to do what your “upper-level you” wants, and bad habits are those that are controlled by your “lower-level you” and stand in the way of your getting what your “upper-level you” wants. You can create a better set of habits if you understand how this part of your brain works. For example, you can develop a habit that will make you “need” to work out at the gym.

Developing this skill takes some work. The first step is recognizing how habits develop in the first place. Habit is essentially inertia, the strong tendency to keep doing what you have been doing (or not doing what you have not been doing). Research suggests that if you stick with a behavior for approximately eighteen months, you will build a strong tendency to stick to it nearly forever.

I read Charles Duhigg’s best-selling book The Power of Habit, really opened my eyes about habits. Duhigg’s core idea is the role of the three-step “habit loop.” The first step is a cue—some “trigger that tells your brain to go into automatic mode and which habit to use,” according to Duhigg. Step two 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.” Repetition reinforces this loop until over time it becomes automatic. This anticipation and craving is the key to what animal trainers call operant conditioning, which is a method of training that uses positive reinforcement. For example, dog trainers use a sound (typically a clicker) to reinforce behavior by pairing that sound with a more desirable reward (typically food) until the dog will perform the desired behavior when it merely hears the click. In humans, Duhigg says, rewards can be just about anything, ranging “from food or drugs that cause physical sensations, to emotional payoffs, such as the feelings of pride that accompany praise or self-congratulation.”

Habits put your brain on “automatic pilot.” In neuroscientific terms, the basal ganglia takes over from your cortex, so that you can execute activities without even thinking about them.