Why did longstreet urge lee not to continue the battle of gettysburg?

During the Battle of Gettysburg, Longstreet pleaded to separate from the enemy line after the first day of battle, in order to effect a strategic flank movement that would position them in the communications line of the Union army, forcing them to attack. Longstreet later said that Lee had agreed before the campaign that this "offensive strategy, defensive tactics" would be a good course of action. Subsequently, however, Lee decided on offensive tactics, fearing perhaps that a move like the one proposed by Longstreet could result in a great loss of morale among the troops. On July 2, the second day of the battle, Longstreet's assault on the federal left was almost successful, but at great cost. On July 3, when Lee ordered Longstreet, against his wishes, to attack the Union center in what is known as "Pickett's charge", the Confederates lost 7,000 men in one hour. Lee blamed himself for the defeat at Gettysburg, but some, like General Jubal Early, insisted that Longstreet's reluctance to follow Lee's plans with enthusiasm was the cause of the defeat.