Nepsis
Nepsis is a concept in Eastern [Orthodox Christian theology|Orthodox Christian theology]. It means wakefulness or watchfulness and constitutes a condition of sobriety acquired following a period of catharsis. St. Hesychios the Priest defines nepsis as "a continual fixing and halting of thought at the entrance to the heart."
Etymology
The term comes from the New Testament's First Epistle of Peter. There nepsis appears in a verb form, in the imperative mood, as an urgent command to vigilance and awakeness: "be alert and awake".Context
Perhaps most associated with Orthodox monasticism, innumerable references to nepsis are made in The Philokalia. Parallels have been drawn between nepsis and Jewish devekut.Relation to asceticism
In Orthodox Christianity, the struggle against the corruption of the passions is conducted through ascetic effort to purify the soul. At the advanced stages this involves "bringing the mind into the heart". Purification of the soul, which is achieved only through the help of divine grace, is pursued through one's efforts to fulfill the commandments of Christ, participation in the Holy Mysteries of the Christian Orthodox Church, private prayer including devotion to the Jesus Prayer, fasting according to the Church calendar, study of Holy Scripture and the lives of the saints, and vigilant watchfulness over the thoughts to prevent sinful thoughts from becoming sinful actions, and then passions.As the Christian becomes purified, in time he reaches the stage of theoria or illumination. At this point, the contemplative life begins. All ascetic practice must be understood as simply the means by which the goal of Christian life is pursued. This is the acquisition of the Holy Spirit, which is called theosis, meaning the "deification" of man. According to St. Athanasius and others, "God became man so that man can become god."