Keeping limits

There was once a man who was a champion wrestler. He had mastered 360 holds and tricks, and used a different one every day of the year. It so happened that he was fond of one of his students, and taught him all his tricks, except one. He kept on postponing the day when he would teach him the last trick.
The boy grew in strength and skill, and no one among his contemporaries was able to challenge him. One day, he boasted in front of the king: "My teacher is unchallenged only because he is older than me and because I respect him as my teacher. Otherwise my strength is not less than his and my skill is quite equal to his."
The King did not appreciate this boasting and ordered a match to take place. They cleared the broad wrestling ground and gathered ministers, courtiers and sportsmen to watch.
The boy charged out into the ring like a mad elephant. His master knew that his pupil was not stronger than him, so he used the 360th hold the he had never taught him. The boy did not know how to counter it. He was helpless. His master raised him with both hands above his head and smashed him to the ground. The crowd cheered wildly.
The King congratulated the champion and ordered a robe of honor to be given to him. He reproached the boy, saying: "You were ill-bred enough to dare to challenge your teacher and how you see how hollow your boast was!"
The boy answered: "O lord of the word! He did not overpower me with his strength but rather because of one trick which he never accepted to teach me. Today this one trick gave him the victory."
The King retorted: "It was just for such a day that he had kept his trick! Have you not heard what the wise say? "Never give a friend such power over you that if one day he tries to be your enemy, he can defeat you."
The teacher betrayed by his pupil said: "There is no such thing as loyalty in this world, or at least no one today knows the meaning of loyalty. Whoever learned a trick from me, finally tried to do me down."