By nature, man is changeable. Therefore, just as one who has fallen into the depths of vice and is enslaved to sin can turn to the good, so one who has been sealed with the Holy Spirit and filled with heavenly gifts is free to return to evil. When some people who have tasted of God’s grace and become communicants of the Holy Spirit can still become careless and not watchful, they grow spiritually feeble and their spiritual light dims, and they become worse than they had been before. This happens not because God changes or the grace of the Spirit goes out, but because the people themselves lose grace, and as a result they are led astray and fall into a multitude of evils.
— Venerable Makary the Great
Stolen from the parish newsletter of Russian Orthodox Cathedral St John the Baptist (September 2010).