They have estimated that in Iraq and Afghanistan, U.S. troops expended a mind boggling 250,000 rounds per enemy soldier killed. A lot of that is suppressive fire, and probably includes training, but still, 250,000 rounds?
I've heard that in all wars, soldiers tend to shoot high. In The Great War (WWI), according to British Lieutenant George Roupell, the only way he could get his men to stop firing into the air was by drawing his sword, walking down the trench, "beating [them] on the backside and ... telling them to fire low"
So, yes, it is exceedingly difficult to prepare men (and women) for war. Having certain skills however, (like those acquired by hunting) will come in very handy if you overcome the mental barrier.