There are three things to beware of through life: when a man is young, let him beware of his appetites; when he is middle-aged, of his passions; and when old, of covetousness, especially.
Only one who bursts with enthusiasm do I instruct; Only one who bubbles with excitement do I enlighten. If I hold up one corner and you do not come back to me with the other three, I do not continue the lesson.