Schulz boils it down to this: If you are conflicted about something, self-help posits that you just have to do what your 'idealized' self wants you to do. But if your could give that self control, then wouldn't you have done that already? Why would we need self- help books if all you had to do was embrace some infallible god-like persona within you?
I think it's because people are naturally flawed, sometimes tragically so. Every day I struggle with trying to be that person who writes every day, goes to the gym, is kind, eats less sugar, and meditates. If a book gives you the framework to be the idealized person you want to be, that's great, but I embrace the struggle. My vices are just as much a part of me as my ideals, one cannot eradicate the other, I'm just hoping that the ideals win out in the end.