"Therefore gird up your minds, be sober, set your hope fully upon the grace that is coming to you at the revelation of Jesus Christ. As obedient children, do not be conformed to the passions of your former ignorance, but as he who called you is holy, be holy yourselves in all your conduct, since it is written, 'You shall be holy, for I am holy,'" 1 Peter 1: 13-16
When we become followers of Christ, we are converted. We cease to be those who wander in the darkness, afraid of the dark. We cease to be those who chase after the temporary pleasures and distractions of the world in a vain attempt to satiate some gnawing desire for happiness, contentment and love. The world fulfill that need. Only God can; and when we come to him, we are changed. We find our joy in the Lord and in keeping his Commandments.
Does that mean that we will no longer sin? Does that mean that if we sin we have not really been converted? No, on both accounts. We are still broken. We are still in need of God's continual grace and mercy. When our conduct carries us away from God, we are called to repent and turn back to him who is always ready to forgive. When we fail, Christ is ready to set us on our feet again, as long as we repent of our sins and seek to live according to his ways. This is not a "Get out of Jail Free Card". We must strive for perfection, even if we know that we will only achieve it at our end when we kneel before Jesus in Paradise.