It is silly to want your children and your wife and your friends to live for ever, for that means that you want what is not in your control to be in your control, and what is not your own to be yours. In the same way if you want your servant to make no mistakes, you are a fool, for you want vice not to be vice but something different. But if you want not to be disappointed in your will to get, you can attain to that.
Exercise yourself then in what lies in your power. Each man’s master is the man who has authority over what he wishes or does not wish, to secure the one or to take away the other. Let him then who wishes to be free not wish for anything or avoid anything that depends on others; or else he is bound to be a slave.