What were common CSA soldiers fighting for?

We all know the CSA started the war to preserve the "peculiar institution", but the Lost Causers are quick to point out that this was rarely, if ever, the cause of the common fighting man.

With my own personal experience in war, I strongly suspect that most common soldiers have no idea what they're fighting for, one way or the other. But, of course, there are plenty of exceptions to the rule.

To what extent did common soldiers within the CSA fight explicitly for the preservation of slavery?