Union with Christ and Sanctification

"Sanctification is not a divine 'zap' that automatically makes the believer irreversibly holy. It is a lifelong battle that requires the saint to lay hold by faith of the victory that Christ has accomplished on the cross and actively to enjoy that victory by living in its reality... Christ has already achieved our victory over sin. But sin does not disappear from us just because we are saved. It does not give up its territory without a fight. If we attempt to fight by ourselves, defeat is certain because sin is much stronger than we are. But if we enter the conflict claiming Christ's victory and our part in it, sin and Satan must flee from us." (Barrett, A Radical Comprehensive Call to Holiness, 102)