Self-control is the acts whereby limits are placed on the self.  The self has appetites that must be curbed.  When the uncontrolled self ends up being controlled by an appetite it becomes idolatry.  If we do not master our appetites, attitudes and predispositions we end up being mastered by them.  The Spirit works His fruit of self-control, but not without our cooperation in self-denial.

“He who is slow to anger is better than the mighty, and he who rules his spirit, than he who captures a city.” (Proverbs 16:32 NASB) “Like a city that is broken into and without walls is a man who has no control over his spirit.” (Proverbs 25:28 NASB)

From “Growing Toward Maturity”, by H. Lamar Smith.