When we receive Christ in Holy Communion, we are united to the Risen Christ and come to share in his divine life. While the appearances of bread and wine remain, the Risen Lord Jesus is actually present as the consecrated bread and wine become He who is actually received in Holy Communion—Body and Blood, soul and divinity.
The Eucharist and its celebration are the source and summit of our Catholic faith. So how do we prepare ourselves for something of this magnitude?
First, we approach the Holy Sacrifice of the Mass by our remote preparation. This includes regular prayer and reading of Scripture, the faithful and loving fulfillment of the daily responsibilities of our state in life, and regular participation in the Sacrament of Penance, including daily repentance of sin by an examination of conscience and recitation of the Act of Contrition.
Second, our attentive proximate preparation includes our prayerful recollection as we come to Mass with fasting from food and drink for at least one hour prior to receiving Holy Communion as our health and age permit. Water and medicine are exceptions to the fast and that the elderly, the infirm, and those who care for them can receive Holy Communion even if they have eaten something within the previous hour.
Proximate preparation also includes dressing appropriately and modestly, as well as, not consuming breath mints, chewing gum, candies and the like while in the Sacrifice of the Mass leading up to reception of Holy Communion (source: USCCB). (7:28)