The soul of a man does violence to itself...

The soul of a man does violence to itself, first of all, when it becomes an abscess and, as it were, a tumor on the universe. For to be vexed at anything that happens is a separation of ourselves from nature, in some part of which the natures of all other things are contained. In the next place, the soul does violence to itself when it turns away from any man, or even moves toward him with the intention of injuring, as happens when people are angry. In the third place, the soul does violence to itself when it is overpowered by pleasure or by pain. Fourth, when it playacts and does or says anything insincerely and untruly. Fifth, when it allows any act of its own and any movement to be without an aim and does anything thoughtlessly and without considering what it is - even the smallest things should be done with reference to an end; and the end of rational animals is to follow the reason and the law of the most ancient city and polity. (Book II)