Chapter 16: How to Stick with Good Habits Every Day
“Named after the economist Charles Goodhart, Goodhart’s Law states, ‘When a measure becomes a target, it ceases to be a good measure.’”

“One of the most satisfying feelings is the feeling of making progress.”

“A habit tracker is a simple way to measure whether you did a habit—like marking an X on a calendar.”

“Habit trackers and other visual forms of measurement can make your habits satisfying by providing clear evidence of your progress.”

“Don’t break the chain. Try to keep your habit streak alive.”

“Never miss twice. If you miss one day, try to get back on track as quickly as possible.”

“Just because you can measure something doesn’t mean it’s the most important thing.”

Chapter 17: How an Accountability Partner Changes Everything
“The inversion of the 4th Law of Behavior Change is make it unsatisfying.”

“We are less likely to repeat a bad habit if it is painful or unsatisfying.”

“An accountability partner can create an immediate cost to inaction. We care deeply about what others think of us, and we do not want others to have a lesser opinion of us.”

“A habit contract can be used to add a social cost to any behavior. It makes the costs of violating your promises public and painful.”

“Knowing that someone else is watching you can be a powerful motivator.”