Sleep is a particular state of nature, an image of death, inactivity of the senses. Sleep is one, but, like desire, its sources and occasions are many: that is to say, it comes from nature, from food, from demons, or perhaps, sometimes, from extreme and prolonged fasting, through which the flesh is weakened and at last longs for the consolation of sleep.
Just as prolonged drinking is a matter of habit, so too from habit comes too much sleeping.
Therefore we must struggle with the question of sleep, especially in the easy days of obedience, because a long-standing habit is difficult to cure.
Let us observe and we shall find that the spiritual trumpet (the commencing of the service) serves as an outward signal for the gathering of the brethren, but it is also the unseen signal for the assembly of our foes. Thus so, some of them stand by our bed and when we get up urge us to lie down again: ‘Wait,’ they say, ‘till the preliminary hymns are finished; then you can go to church.’ Others plunge those standing at prayer into sleep. Some produce severe, unusual pains in the stomach. Others egg us on to make conversation in church.
Some entice the mind to shameful thoughts. Others make us lean against the wall as though from fatigue. Sometimes they involve us in fits of yawning. Some of them bring on waves of laughter during prayer, thereby desiring to stir up the anger of God against us. Some force us to hurry the reading or singing—merely from laziness; others suggest that we should sing more slowly for the pleasure of it; and sometimes they sit at our mouths and shut them, so that we can scarcely open them. He who realizes that he is standing before God will be as still as a pillar during prayer and will pray with heartfelt feeling; and none of the aforesaid demons will make sport of him.
Based on Saint John of the Ladder