It must needs be, as the Apostle reminds us, that a man either ‘renewed in the spirit of his mind’ (Ephesians 4:23), progresses day by day, ‘ever stretching forward to those things which are before’, or, if he be neglectful, the result will follow that he will go backwards and become daily worse and worse.
…the human mind cannot remain constant in one and the same state…of necessity, something is ever either being added…or taken away, and there will never be such perfection found in any creature that it will be wholly free from the danger of change.
…therefore we must with unflagging zeal and care give ourselves to the pursuit of virtue, and constantly occupy ourselves in its practice, lest at any time progress may cease, and regress immediately take its place.
…so then there is no virtue that can be possessed by man without possibility of change, but in order that he may constantly keep it when he has acquired it, he must guard it with the same carefulness and application wherewith it was first gained.
~St John Cassian (Conference with Abbot Theodore)
Prayerful Life 