Depression is one way of anticipating death. If I rehearse death through feeling dead, then I will be able to handle it when it really happens. If I can go to the depths and deaths of depression and recover, I'll get the hang of it so when I die... And during the process, at least I'm involved in something important, something of a life-and-death issue. And if I'm involved in this important struggle, I certainly am not just numbly going through life. After all, Thoreau was right, "Most men lead lives of quiet desperation."
Most Self-Preservation types have a paranoid streak somewhere. That's why their concern is Self-Preservation. The self is under attack in some way. The specific way the self is under attack in the Four strategy is through dull, unimaginative, unrelenting ordinariness. One might as well be dead as stuck here in this (small town, boring relationship, monotonous job) environment. Life without emotional intensity is not really life.
Read Hamlet's soliloquy from the point of view of a Self-Preservation Four and it is quite enlightening. The fundamental question of a Self-Preservation is being: how to be, and more radically, whether to be or not to be.
If that dramatic struggle is an artistic one, they can do without everything but the barest survival necessities while they devote themselves to completing the great American novel or the finest in impressionist painting. The intensity of the struggle contributes to the greatness of the art. This is the artistic temperament. (A note: many beginners assume that every artist is a Four. Artist refers to talent and can occur in any number. The artistic temperament, so called, is frequently a Four, especially the starving artists who can often be Self-Preservation Fours locked in life-and-death-battles, being fought largely in their imaginations).