For in a contest there is much labor needed--and after the contest victory falls to some, to others disgrace. Is the palm ever given or the crown granted before the course is finished? ... Therefore no one can receive a reward, unless he has striven lawfully; nor is the victory a glorious one, unless the contest also has been toilsome.
-St. Ambrose of Milan, Chapter 15, Three Books on the Duties of the Clergy, 4th century


We advance toward humility by means of trials. He who rests on his virtue without suffering tribulation has the door of pride open before him.
-St. Isaac of Syria, Homily 57, in Ascetical Homilies, p. 283, 7th century


But the head of every good endeavor and the guiding force of right actions is perseverance in prayer. By means of it we can daily obtain the rest of the virtues by asking God for them. By this means are engendered in those deemed worthy the fellowship of God’s holiness and of spiritual energy and the attachment of the mind disposed toward the Lord in ineffable love. For the person who daily forces himself to persevere in prayer is enflamed with divine passion and fiery desire from a spiritual love toward God, and he receives the grace of the sanctifying perfection of the Spirit.
-St. Makarios the Great, Homilies 40.2, in Spiritual Homilies, 4th century