My dad and the other men underwent rigorous training. That and the day to day existence of the WWII infantry man was exemplified best by the words of the 6th Army Commanding Officer Lieutenant General Lucien Truscott in his book "Command Missions":

As a cavalry officer, I had long been imbued with the value of speed in military operations. I had, in schools, urged that our own infantry should equal the marching and endurance standards of Roman legions or stonewall Jackson's 'foot cavalry' of Civil War fame...My experience with British Commando training in England confirmed my long held opinions, and led me to believe that such a performance was practicable with modern American soldiers, and furthermore I was to prove to my own, and others, satisfaction that it was one of the best forms of training for battle. p533

I found it was possible to approximate standards for Commando and Ranger training with an entire infantry division, and I noted that the mental determination this required was conducive to the best psychological training. As men reached increasingly difficult standards, self confidence grew. And with this the weeding out of those who could not meet the demands of such rigorous training there developed a pride among those who could. p540

Speed marching was another practical advantage of this high state of training...All battalions had been psychologically prepared to expect hard fighting and heavy losses. And during the campaign they moved so rapidly that opposition was often overcome before it could become fully effective. Speed of execution often made difficult operations seem simple and easy. p540

And in The History of The Third Division In WWII, Lt General Truscott continues:

Yours has been a gallant group and proud your record! Morocco, Tunisia, Sicily, Italy, France, Germany have known your conquering steps. No condition of war has been unknown to you--barren beaches, desert sands, rugged mountains, vine-clad slopes, dense forests, marshy plains, torrid heat, torrential rains, winter snows, mud, ice--you knew them all. Attack and pursuit were your familiar forms of combat. Defense you learned. Only withdrawal and retreat you never needed. Truly your achievements merit well the grateful appreciation of your countrymen. Appendix

One of dad's stories identifies the peak conditioning and the adrenaline level he had at the height of his involvement. One afternoon, he and another soldier were sent out for reconnaissance of a small French town. On arriving in the town, they entered a two story house and climbed to the second floor to get a better look around.

Suddenly, out of nowhere, a German Panther tank rounded the corner and was heading directly for that house since it was located at the end of the street. With no time to use the stairs, they jumped out of the rear second floor window. Landing with a running start, they both scaled a steep wall behind the house and escaped down the road to warn their unit of the German armored presence.

The interesting part of this story is that, later in the war, both of them were again back at this same spot. Neither would take a bet to scale that wall a second time.

From the book Riviera to The Rhine, the same regard of the importance of the infantry is noted:

In the 6th Army Group, perhaps all that can be said is that the American and French infantrymen did the job that had to be done, and it is doubtful that even with better small unit leadership or cohesion they could have accomplished their missions sooner or suffered fewer casualties in the process....Sorting out and mathematically weighing all of the variables on the battlefield is probably an impossible task. Nevertheless, at least the ongoing debate has placed more attention on the capabilities and accomplishments of the average foot soldier, whose exploits are often undocumented and forgotten. p573

LT. General Truscott, in conclusion:

When the American soldiers first came in contact with the German soldier, the latter was already a veteran with a long military tradition, the product of long and thorough military training, led by experienced and capable officers, and equipped with the most modern weapons. The German was then better trained especially for operations in small units, and the quality of his leadership was superior. German soldiers displayed an ingenuity and resourcefulness more American than British. The American quickly adapted himself and learned much from the German. Sicily and southern Italy proved that he had mastered his lessons well. From Anzio on there was never a question of the superiority of American Soldiers. p556