A Zen student came to Bankei and complained: “Master, I have an ungovernable temper. How can I cure it?”
“You have something very strange,” replied Bankei. “Let me see what you have.”
“Just now I cannot show it to you,” replied the other.
“When can you show it to me?” asked Bankei.
“It arises unexpectedly,” replied the student.
“Then,” concluded Bankei, “it must not be your own true nature. If it were, you could show it to me at any time. When you were born you did not have it, and your parents did not give it to you. Think that over.”
Source: Zen Flesh, Zen Bones