For whatsoever is born of God overcometh the world: and this is the victory that overcometh the world, even our faith.
1 John 5:4 (KJV)
The key to living a life of victory is our faith. We use and develop our faith by setting our hearts and minds upon the promises of God, by meditating on them and confessing them until they become real to us. When we are convinced of the reality of something before we can perceive it through our physical senses, we are living in the victory of faith.