Activity tends to grow and to keep on growing, and by this the balance is lost. When we speak we are inclined to speak more and more, and we become so fond of speaking that we like to speak regardless of whether anyone wishes to listen or not. We say what we really do not wish to say; afterwards we wonder why we insulted such and such a person, or why we told him our secret. Sadi, the great Persian poet, says, 'O, intelligent one, of what use is thy intelligence, if afterwards thou repentest?' Whatever we do, whether good or bad, increases in us more and more. If one day a person thinks for five minutes about music or poetry, the next day that thought will continue for half an hour. If one has a little thought of bitterness, unconsciously the thought will grow until one's mind is full of bitterness. Every sin comes about in this way. Zarathushtra distinguished three kinds of sin: the sin of thought, the sin of speech, and the sin of action. To have the thought of bitterness, the thought of evil, is like doing evil; and to speak evil is also like doing evil. When a person commits an evil action, then it is as it were concrete.