The fruit of the Spirit Paul called “self-control” is not “will power.”
The fruit of the Spirit called “peace” doesn’t make me able to find some source of peace. It is the power to be at peace. “Self-control” is the power to surrender your will and your desires and fears and angers and bitternesses to His control. Then, by His power manifesting in you to make you able to will and to do what pleases Him, your self is under control (Philippians 2:12-13).
The increase in discipline that can make you better at accessing self-control is simply disciplining your mind to turn to His strength before deciding or acting. His awesomeness then becomes yours.