Let us call it the master theory of self-help. It goes like this: Somewhere below or above or beyond the part of you that is struggling with weight loss or procrastination or whatever your particular problem might be, there is another part of you that is immune to that problem and capable of solving it for the rest of you. In other words, this master theory is fundamentally dualist. It posits, at a minimum, two selves: one that needs a kick in the ass and one that is capable of kicking.
This model of selfhood is intuitively appealing, not least because it describes an all-too-familiar experience. As I began by saying, all of us struggle to keep faith with our plans and goals, and all of us can envision better selves more readily than we can be them. Indeed, the reason we go to the self-help section in the first place is that some part of us wants to do something that some other part resists.