That even a baptized person loses the grace that he has attained, unless he keep innocency
In the Gospel according to John: “Lo, you are made whole: sin no more, lest a worse thing happen unto you.” Also in the first Epistle of Paul to the Corinthians: “Do you not know that you are the temple of God, and the Spirit of God abides in you? If any one violate the temple of God, him will God destroy.” Of this same thing in the Chronicles: “God is with you, while you are with Him: if you forsake Him, He will forsake you.”
Source: The Treatises of Cyprian (New Advent)