An angel appeared to the shepherds who were keeping watch in the field to announce "good tidings of great joy.... And suddenly there was with the angel a multitude of the heavenly host, praising God, and saying, Glory to God in the highest, and on earth peace, good will toward men." And so, you may well ask, where is this peace and good will the Gospel proclaims? Look around the world today, and you will find little evidence of such a felicitous state of affairs. Is it all just a scam after all, as the atheists might suggest?
Well, we'd probably complain if we were not given a new rope to hang ourselves. Nervertheless... the simple and obvious fact is that life in this fallen world is hard--and sometimes downright brutal. And yet somehow we imagine: in a perfect world, things would be different. And so it might occur to us to wonder: if God really is perfect and all-powerful as we Christians proclaim, why can He not give us such a perfect world?
In other words, if God is truly good, why does He allow all the pain, suffering, and sadness in this world? Why can He not simply wave His magic wand and give us that "peace and good will" the angelic hosts so joyfully and triumphantly proclaim? For surely, an omnipotent God could easily create for us a perfect world devoid of pain and suffering, banishing every trace of sickness and sorrow.
But what sort of world would this be? A world of robots, without free will, programed either for a false, superficial happiness, or else compelled to be good... either the soulless society of Brave New World, or else the totalitarian nightmare of 1984. In either case, it would be a nihilistic world lacking any ultimate meaning or purpose.
Truth be told, the peace that Christ promises His Church is not the mere absence of conflict between nations. It is, rather, an inner peace that enables us to endure with patience the trials and tribulations inevitable in this earthly life on this side of the eschaton, that we may be made worthy in the end of God's eternal Kingdom.
Life is too short and the stakes too high to fritter away the time allotted to us by God in pursuit of an ephemeral "happiness" that cannot, in the end, satisfy the deepest longings of our soul. For truly, to paraphrase St. Augustine, "our hearts are ever restless, till they find their rest in Him."