But we CAN know ourselves, Charles Chu.
And we have lots of good ideas about how the self works.
It is not true that “All self-help theories, model the self in a particular way,” because different theories model the self in different ways. although it is true that we are complex systems, with different, contradictory parts.
At a certain developmental stage, we do become capable of adopting a third person view of ourselves… and then, even a 4th person (at later stages of development that some people never reach).
This allows us to evaluate the results of our own experiments, as Schulz suggests. When these experiments are intentional (not “mutations”), then we call it either science, engineering, design… or maybe art. This the premise of the book Designing Your Life.