Many person might have achieved wisdom had they not supposed that they already possessed it.
Seneca the YoungerCato, being scurrilously treated by a low and vicious fellow, quietly said to him, "A contest between us is very unequal, for thou canst bear ill language with ease, and return it with pleasure; but to me it is unusual to hear, and disagreeable to speak it." There are none more abusive to others than they that lie most open to it themselves; but the humor goes round, and he that laughs at me today will have somebody to laugh at him tomorrow.
Seneca the Younger