Reprinted from Orthodox Prayer Life: The Interior Way with permission of St. Vladimir's Seminary Press.

At times our soul is suffocated and is, as it were, amid the waves; andwhether a man reads in the Scriptures, or performs his liturgy, or approachesanything whatever, he receives darkness upon darkness. He leaves off [prayer]and cannot even draw nigh to it. He is wholly unable to believe that a changewill occur and that he will be at peace. This hour is full of despair and fear;hope in God and the consolation of faith are utterly extinguished from his soul,and she is wholly and entirely filled with doubt and fear.Those who have been tried by the mighty waves of this dark hour knowfrom experience the change that follows upon its completion. God does notleave the soul in these things an entire day, for otherwise she would perish,being estranged from the Christian hope; but he speedily provides her with an"escape" (1 Cor 10.13). But even if the oppression of this darkness should beprolonged, you should expect that a change to the better will proceed swiftlyout of the midst of it.I admonish and counsel you, O man, if you do not have the strength tomaster yourself and to fall upon your face in prayer, then wrap your head inyour cloak and sleep until this hour of darkness pass from you, but do not leaveyour dwelling. This trial befalls those especially who desire to pass their life inthe noetic discipline, and who throughout their journey seek the consolationof faith.
For this reason their greatest pain and travail is the dark hour whentheir mind wavers with doubt. And blasphemy follows hard upon this. Sometimesa man is seized by doubts in the resurrection, and by other thingswhereof we have no need to speak. Many times we have experienced all thesethings, and we have written of this struggle for the comfort of many.Blessed is he who patiently endures these things within the doors [of hiscell]! Afterward, as the Fathers say, he will attain to a magnificent and enduringdwelling. This struggle, however, does not cease immediately, nor in anhour; nor does grace come once and for all and dwell in the soul, but littleby little of one and the other: sometimes trial, sometimes consolation. A mancontinues in these things until his departure. In this life we should not expectto receive perfect freedom from this struggle, nor to receive perfect consolation.For thus is God pleased to govern our life here: that those whojourney in the way should be in the midst of these things. To him be glory untothe ages of ages. Amen. (St Isaac the Syrian, Homilies 50, in The Ascetical Hom-iliesof Saint Isaac the Syrian, pp 241-42)