Has it ever happened to you, after some good deed well done, to feel a surge of strength?
We are used to the idea that when we do something, we give up strength and energy, and when we take food, we restore them. But this is characteristic of the fallen state of human nature, which we consider "natural." According to God's plan, God Himself is the source of life and the giver of strength, while the human person is God's fellow worker and a conductor of His grace into the surrounding world. Thus a person's self-giving turns out to be participation in the source of life and the true filling of the person, because the main thirst of the person is the thirst for love. Jesus shows His disciples an example of such filling by leading the Samaritan woman to a faith that changes her life, and thereby fulfilling the will of the Father who sent Him.