The highest priority God gives us in life is to love him wholeheartedly and to love our neighbors as we love ourselves. Yet, this can be a struggle for the most kind-hearted Christian. Regarding this dilemma, C. S. Lewis wrote:
"But though natural likings should normally be encouraged, it would be quite wrong to think that the way to become charitable is to sit trying to manufacture affectionate feelings. Some people are “cold” by temperament; that may be a misfortune for them, but it is no more a sin than having bad digestion is a sin; and it does not cut them out from the chance, or excuse them from the duty, of learning charity.
The rule for all of us is perfectly simple. Do not waste time bothering whether you “love” your neighbor; act as if you did. As soon as we do this we find one of the great secrets. When you are behaving as if you loved someone, you will presently come to love him. If you injure someone you dislike, you will find yourself disliking him more. If you do him a good turn, you will find yourself disliking him less. There is, indeed, one exception. If you do him a good turn, not to please God and obey the law of charity, but to show him what a fine forgiving chap you are, and to put him in your debt, and then sit down to wait for his “gratitude” you will probably be disappointed. (People are not fools: they have a very quick eye for anything like showing off, or patronage.) But whenever we do good to another self, just because it is a self, made (like us) by God, and desiring its own happiness as we desire ours, we shall have learned to love it a little more, or, at least, to dislike it less.
Consequently, though Christian charity sounds a very cold thing to people whose heads are full of sentimentality, and though it is quite distinct from affection, yet it leads to affection. The difference between a Christian and a worldly man is not that the worldly man has only affections or “likings” and the Christian has only “charity.” The worldly man treats certain people kindly because he “likes” them: the Christian, trying to treat everyone kindly, finds himself liking more and more people as he goes on—including people he could not even have imagined himself liking at the beginning….
Some writers use the word charity to describe not only Christian love between human beings, but also God’s love for man and man’s love for God. About the second of these two, people are often worried. They are told they ought to love God. They cannot find any such feelings in themselves. What are they to do? T he answer is the same as before. Act as if you did. Do not sit trying to manufacture feelings. Ask yourself, “If I were sure that I loved God, what would I do?” When you have found the answer, go and do it."
- C.S. Lewis, Mere Christianity (Macmillan Publishing Company, Touchstone edition, 1996), pp. 116-117.