A second qualification that must be made before we admit to the charge of escapism concerns whether or not our “being too heavenly-minded makes us no earthly good.” If we spend all our time hoping for harps and halos, it is asked, when will we ever find the time to work toward earthly happiness and humanitarianism?
As Kreeft points out, the charge that heavenly-mindedness diminishes earthly goodness is not necessarily true (though in some cases it might be). Let us answer the question with a question: Who is more likely to quit smoking during pregnancy, the mother who plans for an abortion or the one who plans to give birth? The answer should be obvious. Roads that actually lead somewhere are usually better maintained than dead-end ones, and likewise, when our earthly sojourn is seen as just that—a sojourn on the way to our heavenly home—then it is reasonable to assume that this pilgrimage will be taken with great seriousness and care. If death is not the end of the road, but actually ushers us into the presence of the God who gave us life and demands an account of how we lived it, then is it not to be expected that the pilgrim with an eye on his destination will live more purposefully than will the tourist, the goal of whose trip is to get as much bang for his buck? 
In short, we must realize that if we long to live like the divine image-bearers that we are rather than like the animals that the Darwinists want us to be, then the first thing we must do is dwell less upon our past and more upon our future. The chicken is indeed produced by the egg, and, likewise, we are the product of our ancestry in some sense. But all of that pales to the deeper question of what the chicken is for. Sure, the “origin of the species” is important, but not nearly as important as its final destination.
 See http://www.peterkreeft.com/topics/heaven.htm