There are those men who say to repay evil with kindness. But I say, how then are we to repay kindness? Repay kindness with kindness, but repay evil with justice.
The Master said, “What a worthy man was Yan Hui! Living in a narrow alley, subsisting upon meager bits of rice and water—other people could not have borne such hardship, and yet it never spoiled Hui’s joy. What a worthy man was Hui!” (Analects 6.11)
To know, is to know that you know nothing. That is the meaning of true knowledge. When you say something, say what you know. When you don't know something, say you don't know. That is knowledge.
If a man withdraws his mind from the love of beauty, and applies it as sincerely to the love of the virtuous; if, in serving his parents, he can exert his utmost strength; if, in serving his prince, he can devote his life; if in his intercourse with his friends, his words are sincere - although men say that he has not learned, I will certainly say that he has.