18 Hence it is necessary, Venerable Brethren, to revive it once more in the minds of all, for in no other way can individuals and nations attain to peace. Let us, then, bid those who are undergoing distress of whatever kind, not to cast their eyes down to the earth in which we are as pilgrims, but to raise them to Heaven to which we are going: "For we have not here a lasting city, but we seek one that is to come" ( Heb . xiii. 14). In the midst of the adversities whereby God tests their perseverance in His service, let them often think of the reward that is prepared for them if victorious in the trial: "For that which is at present momentary and light of our tribulation worketh for us above measure exceedingly an eternal weight of glory" (II Cor . iv. 17). We must strive by every possible means to revive amongst men faith in the supernatural truths, and at the same time the esteem, the desire and the hope of eternal goods. Your chief endeavours, Venerable Brethren, that of the Clergy, and of all good Catholics, in their various societies, should be to promote God's glory and the true welfare of mankind. In proportion to the growth of this faith amongst men will be the decrease of that feverish striving after the empty goods of the world, and little by little, as brotherly love increases, social unrest and strife will cease.
Source: Ad Beatissimi Apostolorum (Vatican.va)