Never esteem anything as of advantage to you that will make you break your word or lose your self-respect. Book III

Optimism is not only a false but also a pernicious doctrine, for it presents life as a desirable state and man's happiness as its aim and object. Starting from this, everyone then believes he has the most legitimate claim to happiness and enjoyment. If, as usually happens, these do not fall to his lot, he believes that he suffers an injustice, in fact that he misses the whole point of his existence. The World As Will and Representation

Reading is thinking with some one else's head instead of one's own. Parerga and Paralipomena

Chess ... a foolish expedient for making idle people believe they are doing something very clever when they are only wasting their time. The Irrational Knot