"To suspect your own mortality is to know the beginning of terror; to learn irrefutably that you are mortal is to know the end of terror."
(Children of Dune)
But if you make your peace with your own mortality at a relatively young age, it doesn't go over well to be too share-y about that with other people who haven't yet done the same. It doesn't convince them you are wise. It just apparently makes you scary as all hell. Or something.