Just as a physician might say that there very likely is not one single living human being who is completely healthy, so anyone who really knows mankind might say that there is not one single living human being who does not despair a little, who does not secretly harbor an unrest, an inner strife, a disharmony, an anxiety about an unknown something or a something he does not even dare try to know, an anxiety about some possibility in existence or an anxiety about himself, so that, just as the physician speaks of going around with an illness in the body, he walks around with a sickness, carries around a sickness of the spirit that signals its presence at rare intervals in and through an anxiety he cannot explain.

Author: Søren Kierkegaard