Here, Jesus teaches that the believer must persevere to receive complete salvation. Salvation is a gift that cannot be earned or maintained by our own works. It has to be received by faith. However, there is effort on our part to maintain that faith. This is where holiness comes in.
Holiness will not produce relationship with God, nor will a lack of holiness make God turn away from us. He deals with us according to our faith in Jesus, not our performance. Holiness will keep Satan from stealing our faith, while a lack of holiness is an open invitation for the devil to do his worst. A person who wants to endure to the end cannot live a lifestyle that permits Satan free access to him.
Although God is not imputing our sins unto us, we cannot afford the luxury of sin because it allows Satan to have access to us. When a Christian does sin, and allows the devil an opportunity to produce death in his life, the way to stop this is to confess the sin. God is faithful and just to take the forgiveness that is already present in our born-again spirit and release it in our flesh, thereby removing Satan and his strongholds.
Holiness is a fruit and not a root of salvation. That is to say that holiness is a by-product of relationship with God; it does not produce relationship with God. It is the nature of a Christian to walk in the light, not in the dark. When we are rightly informed of who we are and what we have in Christ, then holiness will naturally flow out of us because it is our nature.