His power of knowing, of understanding, of utilizing to the best advantage, is the sign of mastery. But at the same time there is one enemy that man has, and that enemy is limitation; and the spirit of limitation is always a hindrance to realizing the spirit of mastery and practicing it. Those who at some time or other in their lives have realized this principal object for which man is born, have then tried to develop that spirit of mastery in order to defend themselves.