The practice of the presence of God is justly called by spiritual masters the foundation of a spiritual life, which consists in three things: the avoidance of sin, the practice of virtue, and union with God. These three effects the presence of God produces: it preserves the soul from sin, leads it to the practice of virtue, and moves it to unite itself to God by means of holy love.
As to the first effect, the avoidance of sin, there is no more efficacious means of subduing the passions, of resisting temptations and consequently of avoiding sin than the remembrance of God's presence. The angelic Doctor (Thomas of Aquinas) says: "If we always thought that God was looking at us, we would never, or scarcely ever, do what is displeasing in his eyes." And St. Jerome has written that the remembrance of God's presence closes the door against all sins. "The remembrance of God," says the holy doctor, "shuts out all sins." And men will not dare in their presence to transgress the commandments of princes, parents, or Superiors, how could they ever violate the laws of God if they thought that he was looking at them? St. Ambrose relates that a page of Alexander the Great, who held in his hand a lighted torch while Alexander was offering sacrifice in the temple, suffered his hand to be burnt sooner than be guilty of irreverence by allowing the torch to fall. The saint adds, that if reverence to his sovereign could conquer nature in a boy, how much more will the thought of the divine presence make a faithful soul overcome every temptation, and suffer every pain rather than insult the Lord before his face!
All the sins of men flow from their losing sight of the divine presence. "Every evil," says St. Teresa, "happens to us because we do not reflect that God is present with us, but imagine that he is at a distance." The Abbot Diocles went so far as to say that "he who distracts himself from the remembrance of the presence of God becomes either a beast or a devil." On the other hand, the saints by the thought that God was looking at them have bravely repelled all the assaults of their enemies. This thought gave courage to holy Susanna to resist the temptations of the Elders, and even their threats against her life.
Behold the efficacy of the remembrance of the divine presence to make us avoid sins. Let us then always pray to the Lord, saying with Job: Set me beside thee, and let any man's hand fight against me. My God, place me in Thy presence; that is, remind me in every place that Thou seest me, and then let all my enemies assail me: I shall always defeat them. Hence St. Chrysostom concludes: "If we keep ourselves always in the presence of God, the thought that he sees all our thoughts, hears all our words, and observes all our actions will preserve us from thinking any evil, from speaking any evil and from doing any evil."
As to the second effect, the practice of virtue, the presence of God is also a great means. Oh, what valour does a soldier exhibit in the presence of his sovereign! The sole thought that his prince by whom he shall be punished or rewarded is present inspires him with great courage and strength. Thus also when such a religious is in the presence of her Superior, with what exterior recollection does she pray, with what modesty and humility does she treat the sisters; with what care does she execute the directions that she receives! Hence if they reflected that God was looking at all their actions, all religious would do all things well, with a pure intention, without seeking to please any one but God, and without any regard to human respect. St. Basil says that were a person to find himself in the presence of a king and a peasant, his sole concern would be to please the king without any regard to the wishes of the peasant. Thus he that walks in the divine presence is regardless of the pleasure of creatures, and seeks only to please God, who sees him always.
Finally, as to the third effect of the divine presence, that is to unite the soul to God, it is an infallible rule that love is always increased by the presence of the object loved. This happens even among men, although the more they converse together, the more their defects are discovered. How much more shall the love of a soul for God increase if it keeps him before its eyes! For the more it converses with him, the better it comprehends his beauty and amiableness. Morning and Evening meditation are not sufficient to keep a soul united with God. St. John Chrysostom says, that even water, if removed from the fire, soon returns to its natural temperature; and therefore after prayer it is necessary to preserve fervour by the presence of God, and by renewing our affections.
The practice of the presence of God is exercised partly in the operation of the understanding, and party in the operation of the will: of the understanding, in beholding God present; of the will, in uniting the soul to God, by acts of humiliation, of adoration, of love etc.
With regard to the intellect, the presence of God may be practised:
By imagining that our Redeemer, Jesus Christ, is present, that he is in our company, and that he sees us in whatsoever place we may be. We can at one time represent him in one mystery, and again in another: for example now an infant lying in the manger of Bethlehem, and again a pilgrim flying into Egypt; now a boy working in the shop of Nazareth, and again suffering as a criminal in his Passion in Jerusalem, scourged or crowned with thorns, or nailed to a cross. It is necessary to remark, however, that though this method is good, it is not the best, nor is it always profitable: first, because it is not conformable to truth; for Jesus Christ, as God and man together, is present with us only after Communion, or when we are before the Blessed Sacrament. Besides, this mode is liable to illusion, or may at least injure the head by the efforts of the imagination. Hence, should you wish to practice it, you must do it sweetly, only when you find it useful, and without laboring to represent in the mind the peculiar features of our Saviour, his countenance, his stature or color. It is enough to represent him in a confused manner, as if he were observing all we do.
The second method, which is more secure and more excellent is founded on the truth of faith, and consists in beholding with the eyes of faith God present with us in every place, in considering that he encompasses us, that he sees and observes whatever we do. We indeed do not see him with the eyes of the flesh. Nor do we see the air, yet we know for certain that it surrounds us on every side, that we live in it; for without it we could neither breath nor live. We do not see God, but our holy faith teaches that he is always present with us. And as a sponge in the midst of the ocean is encompassed and saturated with water, so says the Apostle, we live in God, we move in God, and we have our being in God. And our God, says St. Augustine, observes every action, every word, every thought of each one of us. Hence, observing all we do, say and think, he marks and registers all, in order to demand an account on the day of accounts, and to give us then the reward or chastisement that we deserve.
The third means of preserving the remembrance of God is to recognize him in his creatures, which have from Him their being, and their power of serving us. God is in the water to wash us, in the fire to warm us, in the sun to enlighten us, in food to nourish us, in clothes to cover us, and in like manner in all other things he has created for our use. When we see a beautiful object, a beautiful garden, or a beautiful flower, let us think that there we behold a ray of the infinite beauty of God, who has given existence to that object. If we converse with a man of sanctity and learning, let us consider that it is God who imparts to him a small portion of His own holiness and wisdom.
The fourth and most perfect means of remembering the divine presence is to consider God within us, in a manner different from that in which he is present in other creatures; in us he is present as in his own temple and his own house. Know you not, says the Apostle, that you are the temple of God, and that the Spirit of God dwelleth in you? Hence our Saviour says that into a soul that loves God, He comes with the Father and the Holy Ghost, not to remain there for a short time, but to dwell in it forever and to establish an everlasting habitation. If, any one love me, . . . my Father will love him, and we will come to him, and will make our abode with him. God is in all places; his presence fills heaven and earth; but He dwells in a particular manner in our souls, and there, as he himself tells us by the mouth of the Apostle, He delights to remain. I will dwell in them, and will walk among them, and I will be their God. There He wishes us to love Him and pray to Him: for he remains in us full of love and mercy, to hear our supplications, to receive our affections to enlighten us, to govern us, to bestow on us his gifts and to assist us in all that can contribute to our eternal salvation.
(Parts Taken From: The True Spouse of Jesus Christ by St. Alphonsus De Liguori)