Everyone wants you to be stupid. Why?
So they can make money from you—is another axiom, or a statement, that wise and smart people are using when they are facing problems and needed to make decisions to protect their personal interest.
The story about the author’s some health problem that she started encountering as she started getting older. Medicine is not an engineering that relays on formulas. Medicine is an art. Just go to 3-4 physicians and you could get 3-4 different diagnosis. How she was using the above axiom as a starting point to analyze her health problems and what decision she make to benefit her, and not some messengers she described in this story.