"My dear Watson," said he, "I cannot agree with those who rank modesty among the virtues. To the logician all things should be seen exactly as they are, and to underestimate one's self is as much a departure from truth as to exaggerate one's own powers.[…]"
↓↓↓ https://en.wikisource.org/wiki/The_Greek_Interpreter
Strengths and deficiencies are discovered only with life experience, over time. In adolescence we often overestimate or underestimate ourselves, due to the play of imagination and conflicting emotions that suddenly impose themselves (biological phenomenon).
"In adolescence we often overestimate or underestimate ourselves" Direct consequence is that most never reach adulthood (they never learn it)
In a sane world adults would teach (indirectly) adolescents to estimate their abilities. In reality adults more often than not make adolescent hate themselves. I'm not talking about my own catastrophic youth here. This is an observation I make almost daily.
the stupid is just a part of the living human contract