St. Nicodemus the Hagiorite: Acquisition and Loss of Grace in Baptism

 No sooner are we baptized than the soul shines brighter than the sun, being purified by the Holy Spirit. And not only to we see the glory of God but we also receive from it a certain splendor just as a piece of silver in the rays of the sun reflects those very rays which it receives. But what a pity! It is only right to sigh here bitterly! For this glory which is ineffable and awesome remains within us only one or two days.¹ For we extinguish it, being led astray by the winter of worldly cares, the dense clouds of which block out its rays. For the care pertaining to living are indeed a heavy winter and even more sullen than winter.

+St. Nicodemus the Hagiorite, from A Handbook of Spiritual Counsel, Chapter 1, The Attributes of the Mind and the Body
¹At the time this was written, most people were still being baptized as adults.

St. Nicodemus the Hagiorite: On the Omnipresence of God

 Our pagan forefathers sought to teach men to avoid shameful deeds by asking them to imagine the presence of some important and revered person. If the imaginary presence of mortal men can avert one from doing evil when found alone, how much more can the true and abiding presence of the true and omnipresent and immortal God, who not only sees the external deeds of men but also knows the inner thoughts and feelings of the heart?

Most foolish then are those who are by themselves alone in an isolated or dark place and who have no self-respect and shame, nor remember the presence of God. The may say: "I am now in this darkness, who can see me?" God condemns such persons as being foolish. "Can a man hide himself in secret places so that I cannot see him?... Do I not fill heaven and earth?" (Jer 23:24). "A man who breaks his marriage vows says to himself, 'Who sees me? Darkness surrounds me, and the walls hid me, and no one sees me. Why should I fear? The Most High will not take notice of my sins.' His fear is confined to the eyes of men, and he does not realize that the eyes of the Lord are ten times brighter than the sun" (Sir 23:18-19).

+St. Nicodemus the Hagiorite, from A Handbook of Spiritual Counsel, chapter 7, On Guarding the Sense of Touch

St. Nicodemus the Hagiorite: On Frequent Communion

I want to ask you this: If at the time of the Mystical Supper one of the Apostles said: "I do not want to receive Communion today," what would the Lord have said? Certainly, I believe that just as He said to Peter at the sacred washing of the feet, "If Is wash thee not, thou hast no part with Me" (John 13:8), He would likewise have said to one not wanting to receive Communion at the Divine Supper, "If thou dost not eat My body, and if thou dost not drink My blood, thou hast no part with Me."
Beloved, the Lord says this very same thing to us now at every Liturgy: "Except ye eat the flesh of the Son of  Man... ye have no life in you" (John 6:53).
+St. Nicodemus the Hagiorite, from Concerning Frequent Communion of the Immaculate Mysteries of Christ, Epilogue

St. Nicodemus the Hagiorite: Resistance to Sin

If you feel sometimes such a strong upsurging of sin that resistance to it will seem impossible and the very zeal to oppose it will appear exhausted, take care, brother, not to give up the struggle, but rouse yourself and stand firm. It is a subterfuge of the enemy, who, with the thought that resistance is hopeless, strives to undermine your firm stand and by making you lay down all your arms to force you to surrender to him. Make your mind see this subterfuge of the enemy more clearly and do not give ground. For so long as your will does not incline toward this passionate urge you are still among the victors, the fighters and slayers of the enemy, even if your sympathy is already ranged on the side of the passion. Nothing and nobody can force your will or steal victory from your hands an overthrow you against your will, no matter how obdurate and bitter the war waged in you by the enemies of your salvation. God endowed our free will with such power, that even if all a man's faculties, the whole world and all the demons rose up in arms against him and attacked him, they could not compel it. It is always left free to desire what they offer or demand, if it so wishes, or not to desire it, if it does not wish. On the other hand, for this very reason his will bears the responsibility for everything and is subject to judgment. Remember this well: no matter how weak and exhausted you may feel, you cannot find excuses for inclining toward a passionate suggestion. Your conscience will tell you the same. So the stronger the attacks the stronger the resistance you must prepare, and never abandon this resolve, repeating on all such occasions the word of command of one of our war leaders: "Watch ye, stand fast..., quit you like men, be strong" (1 Cor 16:13).
+St. Nicodemus the Hagiorite, from Unseen Warfare, chapter 14.

Note: Unseen Warfare was taken from a work originally entitled The Spiritual Combat, by the Roman Catholic scholar Lorenzo Scupoli. It was translated into Greek and edited by St. Nicodemus to conform to Orthodox teaching, and later revised by St. Theophan the Recluse who also renamed it. Thus, to some extent, each of these could be credited with the quotation.