Elder Ephraim of Philotheou: Talk only a little, and be watchful over thoughts

 Do not talk a lot. Stay away from back talk, quarreling, loquacity, and everything that issues from a careless tongue. Drive away evil thoughts and filthy fantasies from your mind as soon as they appear. For when the linger inside the mine and heart, they create a grave condition. Whereas when we are careful at the first appearance of the filthy fantasy and the filthy thought that follows, we remain in peace and enjoy the moral gratification of purity.

Therefore, my children, let us pay attention to ourselves every time various bad thoughts enter, because the same approach applies for every bad thought. Whatever kind is may be, when it finds the nous careless, it enters and creates - corresponding to the passion - the aforementioned unhealthy condition.

Therefore, since a monk is fought primarily by thoughts, the thing that saves him is watchfulness! Watchfulness (nepsis) is derived from the word "nēfo," that is, to be careful, vigilant, alert, and on our guard. When we are careful, vigilant, alert, and on our guard, the house of our soul will be well-kept and we shall save our souls for which we struggle our whole life.

+Elder Ephraim of Philotheou, from Counsels from the Holy Mountain, Chapter 14 On Thoughts Fantasies and Distractions, #9

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