What does it mean that habits reduce willpower requirements?

Automated behavior does not require decision-making energy.

Example: You decide to eat a healthy lunch every day. For the first two weeks, this requires active resistance — you drive past three fast-food restaurants, weigh options at the grocery store, negotiate with yourself about whether today is a good day to start. By week eight, you no longer drive past anything. Your car takes the route to the salad place because that is the route you take at noon. You do not weigh options. You order the same three rotating meals. The decision cost has dropped from significant to zero, and the willpower you used to spend resisting the drive-through is now available for the afternoon strategy session that actually needs it.

Try this: Identify five daily decisions you make repeatedly — what to eat, when to exercise, what to wear, which tasks to start first, when to check email. For each one, design a default: a pre-committed choice that eliminates the decision entirely. Implement one default today and run it for seven consecutive days without deviation. At the end of the week, note two things: how much mental energy the default saved, and what you did with that freed capacity.