What was "The Cause" for Longstreet in The Killer Angels?

Whereas many Confederate leaders and politicians believed
that the Confederate cause was "A Holy War"--a just revolution to rid themselves of the
aggression of the Northern states--General James Longstreet saw things much more simply.
To Longstreet, Lee's "war horse" and an innovator in defensive
tactics,

"...
the Cause was
Victory."

However battlefield
success could be won was Longstreet's goal, and he "did not think much of the Cause." To
Longstreet, the war had become a "nightmare," where he found himself fighting against
men he had known and had grown up with. Additionally, three of his own children had died
of the fever within a week back in Richmond, and Longstreet had become withdrawn. But he
had made his decision to fight with the Confederacy,
and

Once chosen, you put your head down and went on to
win.