Eucharistic union preserves the divine life of grace within us and transforms us.
[O]ur Lord gives Himself as food to preserve within us the divine life of grace; moreover, by means of the union that this Sacrament establishes between our souls and the Person of Jesus…by the charity that this union nourishes, Christ works this transformation that caused St. Paul to say: “I live, now not I but Christ liveth in me.”… (Christ in His Mysteries, Marmion, 351)
Inseparable union with man is the goal of the Incarnation and the Eucharist.
Inseparable union with man was the goal of the Incarnation and is the reason for Christ’s life in the Tabernacle. On the altar, he watches over us with love unquenchable. To requite this love in our own finite way, we must with the full measure of Christ’s life working with us, ever strive for the attainment of that indissoluble union, constraining the God of love, the center of all true life, to draw us wholly to himself, that our lives here may, however imperfectly, adumbrate the joy, the peace, and the glory that will be ours when, with the heavenly hierarchy, we shall chant the eternal hymn, “Holy God. Holy and mighty, One. Holy and Immortal One. Have mercy on us.” (Transforming Your Life Through the Eucharist, Kane, 65)
Christ wills to be in us, in our soul, abiding and working within it.
Without establishing a union as close as that of the Word with His Sacred Humanity, Christ, in giving Himself to us, wills to be in us, by His grace and the action of His Spirit, the principle of all our inner activity: Et ego in eo; He is in the soul, He abides in it, but He is not idle, He wills to work in it, and when the soul remains given up to Him, to His every will, then Christ’s action becomes so powerful that this soul will infallibly be carried on to the highest perfection, according to God’s designs. (Christ in the Life of the Soul, Marmion, 264)
“He who eats my flesh and drinks my blood abides in me, and I in him” Jn 6:56
These words are justly taken to mean transformation into Christ. … That Jesus would abide in man signifies that He becomes intimately present to man, not substantially, but touching by His efficacious contact man’s powers and springs of activity. That man should abide in Jesus means that all his powers are subjected or held close to this Divine influence. This implies that the living energy the soul takes the same direction as that of Christ, and is imbued with His spirit. This is transformation. (The Holy Eucharist, Hedley, 115)
We abide in intimacy but also in reverent adoration
[W]e are…coming into contact with the living God. Yet because this is so, Communion is therefore always simultaneously adoration. (290)
We are not on the same footing. He is the wholly other; it is the majesty of the living God that comes to us with him. Uniting ourselves with him means submitting and opening ourselves up to his greatness. (Theology of the Liturgy, Ratzinger, 290-291)
Reflecting about God is lower than union with God.
The arrival at a knowledge about God in prayer is not comparable in value to even a mere step toward union with God himself. the experience of some degree of closeness with God in any taste, feeling, or sense of possession is not a union with God himself. (Saint John of the Cross, Haggerty, 82)