This is a classic Philokalia text explaining the fundamentals of spiritual life. Written to a young and zealous Christian by St. Mark the Ascetic after he himself had retired to the desert, it focuses upon the method to defeat what St. Mark calls "the three giants of the demonic Philistines": ignorance, forgetfulness, and laziness. St. Mark provides the antidote to these core vices in the medicine of mindfulness of God, real spiritual knowledge, and true ardor. This text is full of practical wisdom for cultivating prayer, and especially is a treasure trove of counsel on how to develop an unceasing spirit of gratitude and thanksgiving so that the Christian might learn to say at all times with the Psalmist, "What shall I give to the Lord in return for all His benefits towards me?"