St Siluan the Athonite says that “all this war happens for humility. The enemies [i. e. demons] fell because of their pride, and they push also us to the loss through the same way. … Some people have grown old in ascesis [monastic life], and yet they have not learned humility and they can not understand why they lack peace and their soul is sad”.
St Makarius the Great advises, “when someone is in trouble and is sad among tempests of passions, he needs not to put himself to despair, because this way sin gets even thicker and enters even deeper, while, when one has always the hope of God, somehow evil gets thinner and leaves like water”.
“Grief knocks at the heaven”, says St. John of the Divine Ladder.
In humility the sword that guards the door of Heaven turns, and ascesis becomes katharsis: “then he rests, blissfully modest, because that which he desired, the Heavenly, embraces him by itself, easily…”, as Hoelderlin describes it.