"This simple truth, that the sole purpose of man's life on earth is to do the will of God, contains in it riches and resources enough for a lifetime. Once you have learned to live with it uppermost in mind, to see each day and each day's activities in its light, it becomes more than a source of eternal salvation; it becomes a source of joy and happiness here on earth.
The notion that the human will, when united with the divine will, can play a part in Christ's work of redeeming all mankind is overpowering. The wonder of God's grace transforming worthless human actions into efficient means for spreading the kingdom of God here on earth astounds the mind and humbles it to the utmost, yet brings a peace and joy unknown to those who have never experienced it, unexplainable to those who will not believe."
From Walter J. Ciszek's book He Leadeth me