In many forms of modern contemplative practice, moderation is suggested. In the Centering Prayer movement, leaders suggest two, twenty minute sessions per day. The same recommendation seems to be present in the TM and Zen communities. The idea is to encourage regular practice, not irregular, long sessions.
Some of the concern, at least from Centering Prayer teachers, is that longer sessions may lead to an overload of intense psychological material being released from the subconscious. For this reason, if a new practitioner wishes to dig deeper, many of these teachers will suggest a ten day retreat in the presence of experienced leaders, who may be able to lead someone through this experience in a safe way.
It is somewhat ironic that the author of The Cloud of Unknowing shows little concern for moderation in prayer. In fact, he encourages none at all. In the following exerpt, the author encourages "the middle path" in virtually all areas of life, but in the work of contemplative love, he wishes it would never cease.
"Now if you ask me what sort of moderation you should observe in the contemplative work, I will tell you: none at all. In everything else, such as eating, drinking, and sleeping, moderation is the rule. Avoid extremes of heat and cold; guard against too much and too little in reading, prayer, or social involvement. In all these things, I say again, keep to the middle path. But in love take no measure. Indeed, I wish that you had never to cease from this work of love.
But as a matter of fact, you must realize that in this life it will be impossible to continue in this work with the same intensity all the time. Sickness, afflictions of body and mind, and countless other necessities of nature will often leave you indisposed and keep you from its heights. Yet, at the same time, I counsel you to remain at it always either in earnest, or, as it were, playfully. What I mean is that through desire you can remain with it even when other things intervene. For the love of God, then, avoid illness as much as possible so that you are not responsible for unnecessary infirmity.
I am serious when I say that this work demands a relaxed, healthy, and vigorous disposition of both body and spirit. For the love of God, discipline yourself in body and spirit so that you preserve your health as long as you can. But if, despite your best efforts, illness overtakes you, be patient in bearing it and humbly wait for God's mercy. This is enough. Indeed, your patience in sickness and affliction may often be more pleasing to God than tender feelings of devotion in times of health."
– The Cloud of Unknowing, Chapter 41
Again, the author commands his student to "beat relentlessly" on the cloud, so that he may experience the healing of God.
"And so stand firmly and avoid pitfalls, keep to the path you are on. Let your longing relentlessly beat upon the cloud of unknowing that lies between you and your God. Pierce that cloud with the keen shaft of your love, spurn the thought of anything less than God, and do not give up this work for anything. For the contemplative work of love by itself will eventually heal you of all the roots of sin. Fast as much as you like, watch far into the night, rise long before dawn, discipline your body, and if it were permitted – which it is not – put out your eyes, tear out your tongue, plug up your ears and nose, and cut off your limbs; yes, chastise your body with every discipline and you would still gain nothing. The desire and tendency toward sin would remain in your heart.
What is more, if you wept in constant sorrow for your sins and Christ's Passion and pondered unceasingly on the joys of heaven, do you think it would do you any good? Much good, I am sure. You would profit no doubt and grow in grace, but in comparison with the blind stirring of love, all this is very little. For the contemplative work of love is the best part, belonging to Mary. It is perfectly complete by itself while all these disciplines and exercises are of little value without it.
The work of love not only heals the roots of sin, but nurtures practical goodness. When it is authentic you will be sensitive to every need and respond with generosity unspoiled by selfish intent. Anything you attempt to do without this love will certainly be imperfect, for it is sure to be marred by ulterior motives. Genuine goodness is a matter of habitually acting and responding appropriately to each situation, as it arises, move always my the desire to please God."
– The Cloud of Unknowing, Chapter 12