"These all died in faith, not having received the things promised, but having seen them and greeted them from afar, and having acknowledged that they were strangers and exiles on the earth.  For people who speak thus make it clear that they are seeking a homeland.  If they had been thinking of that land from which they had gone out, they would have had opportunity to return.  But as it is, they desire a better country, that is, a heavenly one. Therefore God is not ashamed to be called their God, for he has prepared for them a city" (Hebrews 11:13–16, ESV).
"In speaking of this desire for our own far-off country, which we find in ourselves even now, I feel a certain shyness. I am almost committing an indecency. I am trying to rip open the inconsolable secret in each one of you--the secret which hurts so much that you take your revenge on it by calling it names like Nostalgia and Romanticism and Adolescence; the secret also which pierces with such sweetness that when, in very intimate conversation, the mention of it becomes imminent, we grow awkward and affect to laugh at ourselves; the secret we cannot hide and cannot tell, though we desire for something that has never actually appeared in our experience. We cannot hide it because our experience is constantly suggesting it, and we betray ourselves like lovers at the mention of a name. Our commonest expedience is to call it beauty and behave as if that had settled the matter. Wordsworth's expedient was to identify it with certain moments in his own past. But all this is a cheat. If Wordsworth had gone back to those moments in the past, he would not have found the thing itself, but only the reminder of it; what he remembered would turn out to be itself a remembering. The books or the music in which we thought the beauty was located will betray us if we trust to them; it was not in them, it only came through them, and what came and what came through them was longing. These things--the beauty, the memory of our own past--are good images of what we really desire; but if they are mistaken for the thing itself, they turn into dumb idols, breaking the hearts of their worshippers. For they are not the thing itself; they are only the scent of a flower we have not found, the echo of a tune we have not heard, news from a country we have never yet visited. Do you think I am trying to weave a spell? Perhaps I am; but remember your fairy tales. Spells are used for breaking enchantments as well as for inducing them. And you and I have need of the strongest spell that can be found to wake us from the evil enchantment of worldliness which has been laid upon us for nearly a hundred years. Almost our whole education has been directed to silencing this shy, persistent, inner voice; almost all our modern philosophies have been devised to convince us that the good of man is to be found on this earth. And yet it is a remarkable thing that such philosophies of Progress or Creative Evolution themselves bear reluctant witness to the truth that our real goal is elsewhere. When they want to convince you that earth is your home, notice how they set about it. They begin by trying to persuade you that earth can be made into heaven, thus giving a sop to your sense of exile in earth as it is. Next, they tell you that this fortunate event is still a good way off in the future, thus giving a sop to your knowledge that the fatherland is not here and now. Finally, lest your longing for the transtemporal should awake and spoil the whole affair, they use any rhetoric that comes to hand to keep out of your mind the recollection that even if all the happiness they promised could come to man on earth, yet still each generation would lose it by death, including the last generation of all, and the whole story would be nothing, not even a story, for ever and ever."
~C. S. Lewis, "The Weight of Glory," The Weight of Glory, pp. 31-32, emphasis mine