An artist who lacks the power of self-criticism accomplishes but little. It is good if your work stands higher than your own opinion of it; bad if it is on the same level. But it is a great disaster if your work stands lower than your judgment of it.

He who wishes to be rich in a day will be hanged in a year.

A clever man without wisdom is like a beautiful flower without fragrance.

If you find from your own experience that something is a fact and it contradicts what some authority has written down, then you must abandon the authority and base your reasoning on your own findings.

Time stays long enough for anyone who will use it.

Though I may not . . . be able to quote other authors, I shall rely on that which is much greater and more worthy - on experience.

Learning acquired in youth arrests the evil of old age; and if you understand that old age has wisdom for its food, you will so conduct yourself in youth that your old age will not lack for nourishment.