Any couch-potato who is well schooled in the viewing of History Channel documentaries about GIs during W.W. II can tell you that this diverse soldiery had one strong psychological element in common: they could not envision failure. The power of positive thought is still very much a vital particle ingrained within the psyche of today's recruit training within the behemoth that is the American military. This is the topic of the attached magazine article from 1918; it concerns the teaching philosophy of Major Herman J. Koehler (1859 – 1927) and how it applied to the training of U.S. Army officer cadets during the First World War. The Major believed deeply that "there is no limit to human endurance".
Read what the U.S. Army psychologists had to say about courage.