The New York Times wrote a fascinating piece about Ernie Pyle, who was essentially the Walter Cronkite of WWII and was there for the invasion.
For those who can't see the article, here's a key quote:
Until D-Day, war had largely been an exhilarating experience for Pyle, terrible but often uplifting. Ten days after the landings, the awfulness of all the death he was witnessing in the “thousands of little skirmishes” in the hedgerow country of Normandy was carving away at his mental state. He reported having knots in his stomach from “constant tenseness and lack of sleep.” In a letter back home, he confided that he had to “continually fight an inner depression over the ghastliness of it all.” “Sometimes,” he wrote to Miller on June 29, “I get so obsessed with the tragedy and horror of seeing dead men that I can hardly stand it. But I guess there’s nothing to do but keep going.”