Willpower is concrete, not ethereal. When you do something, you demonstrate your willpower, and it becomes all the easier to have the same power of will the next time.
Abhyasa (practice) is a dedicated, unswerving, constant, and vigilant search into a chosen subject pursued against all odds in the face of repeated failures, for indefinitely long periods of time.
Love begets courage, moderation creates abundance and humility generates power. Courage without love is brutish. Abundance without moderation leads to over-indulgence and decay. Power without humility breeds arrogance and tyranny.
