C. S. Lewis wrote in Mere Christianity (Book III, Ch. 10, “Hope”),
The Christian says, ‘Creatures are not born with desires unless satisfaction for those desires exists. A baby feels hunger: well, there is such a thing as food. A duckling wants to swim: well, there is such a thing as water. Men feel sexual desire: well, there is such a thing as sex. If I find in myself a desire which no experience in this world can satisfy, the most probable explanation is that I was made for another world. If none of my earthly pleasures satisfy it that does not prove that the universe is a fraud. Probably earthly pleasures were never meant to satisfy it, but only to arouse it, to suggest the real thing. If that is so, I must take care, on the one hand, never to despise, or be unthankful for, these earthly blessings, and on the other, never to mistake them for the something else of which they are only a kind of a copy, or echo, or mirage. I must keep alive in myself the desire for my true country, which I shall not find till after death; I must never let it get snowed under or turned aside; I must make it the main object of life to press on to that other country and to help others to do the same.”
This desire is something I cannot lose– nor do I want to. Often I fall into the first extreme, becoming unhappy with earth and everything that is now wrong with it. Lately I’ve been inspired to value this desire in the right way. God’s kingdom is not something far out in some vague concept of “eternity” with no bearing on the present. The Kingdom of God is being established in this age. God has intentionally placed us on earth and commanded us to advance His kingdom now, every day. May I continually surrender more and more of myself to God, and may I help other hearts find their citizenship in the country that is to come. Even if it’s hard, or confusing, or painful, I know that the desire of my heart will be fulfilled, and when it is, every second in the present broken age will be more than worth it.
I particularly like this song, which is inspired by C. S. Lewis and several passages from the Bible: