St. Paisios of Mount Athos: On overcoming bad habits

 Geronda, can a bad habit be broken immediately?

First of all, man must realize that such a habit is harmful to him, and then he must be willing to struggle to break the habit. One must have a lot of willpower in order to be able to break a bad habit al at once. Just as the rope rubs against the edge of the well and over the years forms a small groove that holds the rope in place, every habit forms a groove in the heart, making them difficult to get rid of. This is why we must be very careful not to develop bad habits, because it takes a lot of humility and great willpower to overcome them. Father Tychon on the Holy Mountain used to say, "my child, a good habit equals virtue; a bad habit equals passions."

In any case, I have found that when a man while struggling, continues to make the same mistakes and does not change, the reason is usually egoism, self-love and self-interest. Humility and love are missing, thus blocking divine intervention. The person himself does not allow God to help him. If, for example, God helps him overcome a particular passion, such a person will selfishly take credit for it and assume that it was his own achievement, without any help from God.

+St. Paisios of Mount Athos, from Spiritual Counsels volume 3, Spiritual Struggle, part 3 chapter 1.

St. Nikolai Velimirovich: Our true humanity is found in doing God's will

 No single man on earth has ever been able to live by his own will and remain a man. "Man" cannot be synonymous with "self-will"; a man, a true man, means total submission to a higher will, the discerning and infallible will of God.

+St. Nikolai Velimirovich, from Homilies volume 2, Homily for the 32nd Sunday after Pentecost.

St. Joseph (Litovkin) of Optina: That which is imposed is difficult

A woman said to [Elder Joseph], "Give me a rule of prayer; but I fear I'll find it difficult." The Elder answered, "That which is imposed is always difficult." Thereupon he told about Archimandrite Isaaky, who while living world was preparing for monasticism by ascetic feats; he did a thousand prostrations daily. After he entered the monastery, he told the Elder Lev about this and he had him do fifty prostrations instead of a thousand. In a short time he came to the Elder and said, "Forgive me, Batiushka, I'm ashamed to confess it, but for some reason I can't do fifty prostrations." The Elder had him do twenty-five. A little time passed and he again appeared before the Elder and said that could in no way understand why when he was living in the world he had been doing a thousand prostrations, whereas here he couldn't do even twenty-five. Then the Elder Lev explained to him: "In the world the enemy was helping you. You did them and became proud of it; but here you are doing them not of your own will, but from obedience. Now you can recognize your feebleness and are being humbled; that is why it is difficult."
+St. Joseph (Litovkin) of Optina, from Elder Joseph of Optina, Chapter V, The Elder Joseph's Instructions.