Discourses, "About Freedom" (§5)

“When you have made this preparation, and have practised this discipline, to distinguish that which belongs to another from that which is your own, the things which are subject to hindrance from those which are not, to consider the things free from hindrance to concern yourself, and those which are not free not to concern yourself, to keep your desire steadily fixed to the things which do concern yourself, and turned from the things which do not concern yourself; do you still fear any man? No one.”