Vivid mindfulness of death embraces many virtues. It begets grief; it promotes the exercise of self-control in all things; it is a reminder of hell; it is the mother of prayer and tears; it induces guarding of the heart and detachment from material things; it is a source of attentiveness and discrimination. These in their turn produce the twofold fear of God.
In addition, the purging of impassioned thoughts from the heart embraces many of the Lord’s commandments. The harsh hour-by-hour struggle in which so many athletes of Christ are engaged has as its aim precisely this purging of the heart.
St. Philotheos of Sinai Forty Texts on Watchfulness, Philokalia, V3.30.