"But Lee’s inaction after Fredericksburg was, as we have called it, an unhappy or negative blunder. Undoubtedly the greatest positive blunder of which he was ever guilty was the unnecessary onslaught which he gratuitously made against the strong position into which, by accident, General Meade fell back at Gettysburg. We have good reason for saying that during the five years of calm reflection which General Lee passed at Lexington, after the conclusion of the American war, his maladroit manipulation of the Confederate army during the Gettysburg campaign was to him a matter of ceaseless self reproach.
"'If,' said he, on many occasions, 'I had taken General Longstreet’s advice on the eve of the second day of battle of Gettysburg, and filed off the left corps of my army behind the right corps, in the direction of Washington and Baltimore, along the Emmitsburg road, the Confederates would to-day be a free people.'"
Source: From Manassas to Appomattox
This article should be read with a certain amount of caution. It is not guilty of intentionally delivering blatantly false information, but it does sometimes take a stance that is more critical of Lee than he may have deserved. The "blunder at Fredericksburg" alluded to in the opening sentence, as most scholars of the war are aware, was not a blunder or a mistake in the traditional sense. Lee was forced to meet Burnside around Fredericksburg, and his position -- mainly due to the Union cannon on Stafford Heights across the river -- did not allow him to pursue the Federals after their bloody repulse without risking his own destruction.
Fredericksburg was a battle whererin the Confederates were forced to rely on Union mistakes to achieve their advantages. When Burnside stopped making mistakes, Lee had no more advantages to take.
Commentary
Excerpt of an article from Eclectic Magazine (later Century Magazine) published in May of 1872 regarding comments Lee supposedly made about his own performance at Gettysburg: