St Maximos the Confessor: Stages of spiritual growth

Those who still fear the war against the passions and dread the assaults of invisible enemies must keep silent; in their struggle for virtue they must not enter into disputes with their enemies but through prayer must entrust all anxiety about themselves to God. To them apply the words of Exodus: "The Lord will fight for you, and you must be silent" (Ex 14:14). Those, secondly, who have been released from the enemy's attacks and who genuinely seek instruction in the ways of acquiring the virtues, need only to keep the ear of their mind open. To them Scripture says, "Hear O Israel" (Deut 6:4). Thirdly, those who as a result of their purification ardently long for divine knowledge may commune with God freely. To them it will be said, "What is it that you are calling to Me?" (Ex 14:15 LXX). Thus, he who is commanded to keep silent because of his fear should seek refuge in God; he who is commanded to listen should be ready to obey the commandments; and he who pursues spiritual knowledge should call ceaselessly to God, beseeching Him for deliverance from evil and thanking Him for communion in His blessings.
+St Maximos the Confessor, from First Century  on Theology, #30, in The Philokalia, Volume 2.

Abba Isaiah of Scetis: Not judging one's neighbor

Not judging one's neighbor is a protection for those who struggle in knowledge, but blaming one's neighbor destroys this protection in ignorance. Taking care of one's tongue¹ is the sign a person who practices the virtues. Not controlling one's tongue shows that a person has no inner virtue. Goodness gives rise to purity. Distraction give rise to passions, and hardheartedness gives rise to anger. Discipline of the soul is hatred of distraction, and disciple of the body is poverty. The fall of the soul is loving distraction, and its rise is silence in knowledge. Excessive sleep disturbs the passions within the body, and vigil in measure is the heart's salvation. Too much sleep thickens the heart, but vigil in measure refines it. It is better to sleep in silence and knowledge, than to keep vigil with idle talk. Compunction calmly expels all evil. Not offending your neighbor's conscience gives rise to humility. Human glory very gradually gives rise to pride. Loving to boast expels knowledge.
+Abba Isaiah of Scetis, from Ascetic Discourses, Discourse 16 On the Joy that Comes to the Soul that Desires to Serve God.

¹ St. John Climacus, from The Ladder, Step 22