The doctrine of the Second Coming has failed, so far as we are concerned, if it does not make us realize that at every moment of every year in our lives Donne’s question “What if this present were the world’s last night?” is equally relevant.
Sometimes this question has been pressed upon our minds with the purpose of exciting fear. I do not think that is its right use. I am indeed far from agreeing with those who think all religious fear barbarous and degrading and demand that it should be banished from the spiritual life. Perfect love, we know, casteth out fear. But so do several other things—ignorance, alcohol, passion, presumption, and stupidity. It is very desirable that we should all advance to that perfection of love in which we shall fear no longer; but it is very undesirable, until we have reached that stage, that we should allow any inferior agent to cast out our fear. The objection to any attempt at perpetual trepidation about the Second Coming is, in my view, quite a different one: namely, that it will certainly not succeed. Fear is an emotion and it is quite impossible—even physically impossible—to maintain any emotion for very long. A perpetual excitement of hope about the Second Coming is impossible for the same reason. Crisis-feeling of any sort is essentially transitory. Feelings come and go, and when they come a good use can be made of them: they cannot be our regular spiritual diet.
What is important is not that we should always fear (or hope) about the End but that we should always remember, always take it into account.
C.S. Lewis, "The World's Last Night" (1960)