From John Eldredge's "The Sacred Romance":
If for all practical purposes we believe that this life is our best shot at happiness, if this is as good as it gets, we will live as desperate, demanding, and eventually despairing men and women. We will place on this world a burden it was never intended to bear. We will try to find a way to sneak back into the Garden and when that fails, as it always does, our heart fails as well. If truth be told, most of us live as though this life is our only hope.
In his wonderful book The Eclipse of Heaven, A. J. Conyers put it quite simply: “We live in a world no longer under heaven.” All the crises of the human soul flow from there. All our addictions and depressions, the rage that simmers just beneath the surface of our Christian facade, and the deadness that characterizes so much of our lives has a common root: We think this is as good as it gets. Take away the hope of arrival and our journey becomes the Battan death march. The best human life is unspeakably sad. Even if we manage to escape some of the bigger tragedies (and few of us do), life rarely matches our expectations. When we do get a taste of what we really long for, it never lasts. Every vacation eventually comes to an end. Friends move away. Our careers don’t quite pan out. Sadly, we feel guilty about our disappointment, as though we ought to be more grateful.
Of course we’re disappointed—we’re made for so much more. “He has also set eternity in the hearts” (Eccl. 3:11). Our longing for heaven whispers to us in our disappointments and screams through our agony. “If I find in myself desires which nothing in this world can satisfy,” C. S. Lewis wrote, “the only logical explanation is that I was made for another world.”