An inferiority complex
Private Milton went to psychiatrist and complained: "I have an inferiority complex.""Nothing I can do for you", said the doc.
"In the Army privates don't have an inferiority complex... they're just inferior..."
An old man saw a very tired infantryman resting after a hard foot march. The man said with disdain: "When I was of your age I thought nothing of a ten-mile hike."
"Well, I don't think much of it either," replied the GI.