No man is free who is not master of himself.
Epictetus
Can I make you happy, mad, or sad? If yes, then I’m your master. Can I, or perhaps an object of your desire, cause you to act on your feelings of greed or jealousy? If yes, then we are your master. Do your feelings correlate or interfere with your ruling principles and your actions parallel to them? If yes, then they are your master.