As most of you who've studied the War of 1861-1865, Robert E. Lee and the Army of Northern Virginia went a "bridge too far" (thank you, Cornelius Ryan). He violated the prime directive of the Confederacy, which was to force the Union Army to conduct an expensive offensive war, and allow the Confederacy to fight defensively, a far less expensive method of conducting war.
Lee was very much out of his element at Gettysburg. He was blind, since his cavalry commander, JEB Stuart, was out of contact, and he had a poor location for a fight, since the Union was able to reinforce and resupply its troops by rail, within a day. Not that Lee intentionally picked a poor location, but it was a poor location nonetheless.
Lee would have been tentative, but I agree that Sheen's downfall was the accent. The other "over-emoter" was Stephen Lang's George Pickett.
There were lots of subsidiary actions during the three days, but Brigadier General John Buford's actions the first day, and stopping the Confederate Army, is the most underrated accomplishment of the entire battle.