The Church's sacraments are ordained for helping man in the spiritual life. But the spiritual life is analogous to the corporeal, since corporeal things bear a resemblance to spiritual. Now it is clear that just as generation is required for corporeal life, since thereby man receives life; and growth, whereby man is brought to maturity: so likewise food is required for the preservation of life. Consequently, just as for the spiritual life there had to be Baptism, which is spiritual generation; and Confirmation, which is spiritual growth: so there needed to be the sacrament of the Eucharist, which is spiritual food.
- St. Thomas Aquinas
The Sacrament of the Eucharist is traditionally the final Sacrament of Initiation, although the current practice is to receive this sacrament before being Confirmed. Each one of us has an infinite desire for truth and goodness but we are finite creatures. God made us to hunger for Him who is True and Good. He has not left us frustrated in our desire because in the Holy Sacrifice of the Mass, God chooses to transubstantiate bread and wine into the Body, Blood, Soul, and Divinity of our Blessed Lord. He then communicates Himself to us in Holy Communion.