Kierkegaard in The Sickness Unto Death:
A person can go on living fairly well, seem to be a human being, be occupied with temporal matters, marry, have children, be honored and esteemed — and it may not be detected that in a deeper sense this person lacks a self. Such things do not create much of a stir in the world, for a self is the last thing the world cares about and the most dangerous thing of all for a person to show signs of having. The greatest hazard of all, losing one’s self, can occur very quietly in the world, as if it were nothing at all. No other loss can occur so quietly; any other loss — an arm, a leg, five dollars, a wife, etc. — is sure to be noticed.