Prayer is…

…the refuge of help, a source of salvation, a treasury of assurance, a haven that rescues from the tempest, a light to those who are in darkness, a staff of the infirm, a shelter in time of temptations, a medicine at the height of sickness, a shield of deliverance in war, an arrow sharpened against the face of the enemies, to speak simply: the entire multitude of these good things is found to have its entrance through prayer.

St. Isaac the Syrian. Ascetical Treatise 8 (68), as quoted by Hilarion Alfeyev, The Spiritual World of Isaac the Syrian (Cistercian Publications, 2000), p. 144