The Sacrament of Holy Communion
The third of the three sacraments of initiation, the Sacrament of Holy Communion is the reception of Christ's Body and Blood. This sacrament is the source of great graces that sanctify us and help us grow in the likeness of Jesus Christ.
In Holy Communion, we are eating the True Body and Blood of Jesus Christ, without which "you shall not have life in you" (John 6:53).
Receiving Holy Communion worthily brings us graces that affect us both spiritually and physically. Spiritually, our souls become more united to Christ, both through the graces we receive and through the change in our actions that those graces effect. Frequent Communion increases our love for God and for our neighbor, which expresses itself in action, which makes us more like Christ.
Because of the intimate connection of the Sacrament of Holy Communion to our life in Christ, we must be free of any grave or mortal sin before receiving it, as St. Paul explained in 1 Corinthians 11:27-29. Otherwise, as he warns, we receive the sacrament unworthily, and we "eateth and drinketh damnation" to ourselves.