Monasticism:

Everything that is instrumental for receiving God’s incorruptible grace is a sacrament. In this sense, we could say that our entire Church is a sacrament. The monastic profession never sought to be acknowledged as one of the sacraments of the Church, as this would put its charismatic character at risk. Monasticism is the closest imitation of the path of Christ - of His kenotic descent and humiliation, and His glorious ascent above the heavens, by which all the gifts of the Holy Spirit came down as rain upon the earth. For this reason, institutionalisation would only occasion vanity and pride, as sometimes happens with holy priesthood.

By avoiding being recognised as an institution, monasticism remains hidden from the eyes of this world, and this allows it to keep its perfect and absolute freedom to exist purely on the spiritual plane, governed exclusively by the power of the Holy Spirit. If monasticism were to become an institution, it would cease to be a life outside the camp of this world (Heb. 13:14); it would lose its charismatic power of humility and its prophetic and paradoxical character, whereby it maintains the knowledge of God on earth.

— Excerpt from: Monasticism: The All-Embracing Gift of the Holy Spirit (An Approach to the Monastic Legacy of Saint Sophrony) • Introduction (p. 13) Archimandrite Zacharias Zacharou