built truth
noun phrase
A lesson that cannot be taught or revealed but can only be learned through personal experience and reasoning.
“Aurelie asked me what I thought of her shiny new boyfriend today."
“Did you tell her what you told me? That he’s clearly going to break her heart and she needs to be single for a while?"
“Of course not! Those are built truths. If I tried to tell her, the only effect would be that she liked me less. No, I just smiled and nodded. She’ll figure this stuff out herself eventually.”