In "why soldiers won't talk" by John Steinbeck

Soldiers protect themselves by desensitizing. Steinbeck describes it almost as if it's an out of body experience. Senses dull, vision blurs, hunger disappears, and the world seems as if it's moving in slow motion.... even though it's moving faster than normal.

This is how you feel after a few days of constant firing. Your skin feels thick and insensitive. There is a salty taste in your mouth. A hard, painful know is in your stomach where the food is undigested. Your eyes do not pick up much detail and the sharp outlines of objects are slightly blurred. Everything looks a little unreal. When you walk, your feet hardly seem to touch the ground and there is a floaty feeling all over your body. Even the time sense seems to be changed. Men who are really moving at a normal pace seem to take forever to pass a given point. And when you move it seems to you that you are very much slowed down, although actually you are probably moving more quickly than you normally do.