The Law means that we live according to the Will and Love of God.
Why is a Master perfect of health and mind, body and soul? Because a Master lives according to the Law in perfection, would never not even think of not living according to the Law. Because a Master is so full with God, the Will of God, the will of soul, that He or She can do nothing but living the Will of God.
Self-sacrifice, which means consciously doing it for Him.