Core principle: make the cues of good habits obvious, make the cues of bad habits invisible.

Tactics for building good habits:

• Put the book on your pillow (reading habit)
• Put the guitar on a stand in the middle of the room (practice habit)
• Place fruit on the counter, not in the crisper drawer (eating habit)
• Leave your journal and pen on your desk (writing habit)
• Set out workout clothes the night before (exercise habit)
• Put a glass of water on your nightstand (hydration habit)

Tactics for breaking bad habits:

• Unplug the TV and put the remote in a drawer (less TV)
• Delete social media apps from your phone (less scrolling)
• Leave your phone in another room while working (less distraction)
• Don't keep junk food in the house (less snacking)

The "one space, one use" principle: Designate specific areas for specific activities. Your desk is for work. Your couch is for relaxation. Your bed is for sleep. When contexts mix, habits compete, and the easier behavior wins. If you eat, watch TV, and work from your couch, that space has no clear behavioral signal. Separate the contexts to strengthen the cues.

The Anne Thorndike hospital cafeteria study: Researchers at Massachusetts General Hospital redesigned the cafeteria layout. They placed water bottles in baskets beside the food stations and in every refrigerator (previously only in one area). No education campaign, no lectures about healthy drinking. Result: water sales increased 25.8% over three months, while soda sales dropped 11.4%. The environment changed the behavior without anyone making a conscious "healthy choice."

Environmental cues are contextual, not rational. You don't decide to check your phone — you see it on the desk and pick it up. You don't decide to snack — you walk past the pantry and grab chips. Changing the environment changes the decision landscape before willpower is even required.