Internal conflicts like diet failures happen because different sub-personalities make decisions - the part that commits to a diet isn't the same part that wants donuts later

Eben provides a specific example: 'If a part of us gets all motivated and says, I'm gonna go on a diet... later on, when you're driving by the donut shop and a different part of you is in the pilot's chair, and it says, I want donuts. Well, it doesn't really care what the other part decided because now this part's in control.'