Søren Kierkegaard (translated by Hong & Hong):
If Abraham had not had faith, then Sarah would surely have died of sorrow, and Abraham, dulled by grief, would have smiled at [his desire for the promise] as at a youthful dream. But Abraham had faith, and therefore he was young, for he who always hopes for the best grows old and is deceived by life, and he who is always prepared for the worst grows old prematurely, but he who has faith—he preserves an eternal youth.
Fear and Trembling
“Eulogy on Abraham”
And even if a person became a thousand years old, he still would not be old enough to dare to speak of [the eternal] in any other way than the young speak of it—with fear and trembling. In relation to the eternal, a person does not in a temporal sense grow older than the eternal, therefore not in the sense of pastness either. No, human language calls it maturity and an advantage to have outgrown, as an adult, the childish and the youthful, but to want at any time to have outgrown the eternal is called falling away from God and perdition, and only the life of the ungodly ‘will be like the snail, which dissolves into slime as it goes along’ (Psalm 58:8).
Upbuilding Discourses in Various Spirits
Part One: An Occasional Discourse, “On the Occasion of a Confession”