In any field, there are a few ideas that are core to understanding everything else. Biology makes little sense without evolution . Physics without symmetries and conservation laws is baffling. All mathematics can be built out of sets .

Self-improvement isn't usually regarded as an intellectual field. It's mostly an assortment of various gurus and pundits' suggestions on how you ought to be more successful, happier or wise. Thus it might seem like self-improvement doesn't really have core ideas at all-just opinions.