For someone who loves the body, mortal life, sensual pleasure, and the material world, separation from them is death; but for someone who loves holiness, God, the immaterial world and virtue, true death is for the mind to be separated from them even briefly. If the eyes of a person who can see sensible light are closed for an instant or covered by someone else, he suffers and is distressed and cannot bear it, especially if he was looking at something important or unusual. But is someone is illumined by the Holy Spirit and, whether asleep or awake, sees spiritually those blessings that ‘the eye has not seen, and the ear has not heard, and man’s heart has not grasped’ (1 Corinthians 2:9), and ‘that angels long to glimpse’ (1 Peter 1:12), how much more will he suffer and be tormented if he is torn away from the vision of these things? For this will seem to him like death, a veritable exclusion from eternal life.
~St Symeon the New Theologian
Prayerful Life 