I had to cut this from a sermon I’m working on, so I’ll share it here, instead:
‘Those who desire to free themselves from their corruption ought to pray not merely from time to time but at all times; they should give themselves always to prayer, keeping watch over their intellect (nous) even when outside places of prayer. When someone is trying to purify gold, and allows the fire of the furnace to die down even for a moment, the material which he is purifying will harden again. So, too, a man who merely practises the remembrance of God from time to time, loses through lack of continuity what he hopes to gain through his prayer.’ –‘On Spiritual Knowledge’, 97, Philokalia 1, pp. 293-94.