On Spiritual Education:

The Christian must unremittingly care for his spiritual education for which he was born anew in the holy font through the Holy Spirit, received spiritual regeneration, was sealed with chrism, or the seal of the Holy Spirit, and was made worthy of the right to communicate in the Most immaculate Blood of Christ. According to God's intent, the holy Church is the first and most lawful educator of Christian souls. There is no more important work than that of Christian education. Judge and understand for yourselves how dear are these rational, immortal souls unto God, which were redeemed by the Blood of the Son of God Himself, which were called out of the darkness of ignorance into the light of the knowledge of God by the Lord Himself, which were betrothed and united to the Lord as pure virgins to a most pure Bridegroom! How dear is the salvation of these souls, to whom He offers His most immaculate Body and most pure Blood as food and drink, whom He Himself undertook to educate spiritually through these wonderful, dreadful, life-creating and deifying Mysteries! Devote yourselves, all of you, to your spiritual education with all attention and diligence; devote yourselves to thoughts concerning God, to prayer, self-investigation, self-condemnation, with self-amendment in every way; exercise yourselves in the virtues of meekness, humility, obedience, patience, compassion, chastity, simplicity, and guilelessness; and cut off all sinful thoughts, lusts, habits, and passions.
St. John of Kronstadt (On the Church)