“If you’re walking along the edge of a cliff, and you don’t know it’s the edge of a cliff, you have perfect confidence. (…) Then you have to be very careful not to listen to anybody. You have to remember your old ignorance. You have to ask for the impossible with the same cheerfulness that you did when you didn’t know what you were talking about.”
—Orson Welles
Bertrand Russell said: “The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt”
according to the quote here, that happens only because the intelligent people is (are?) aware of the cliff.