The Eucharist is the “sign” and “cause” of our communion with God and our unity as the People of God. In the Eucharist, we “unite ourselves with the heavenly liturgy” and with one another. Together transformed, we are then sent forth to fulfil God’s will in our daily lives (Catechism of the Catholic Church [CCC], nos. 1325-26, 1332). In this way, the Eucharistic Liturgy is social in nature. It is the celebration through which God draws us into communion with himself and with others, forming and transforming us to live as the Body of Christ in the world. from:
The Eucharistic Liturgy, Formed, Transformed and Sent, United States Conference of Catholic Bishops
Special care is taken in the preparation for and the reception of First Holy Eucharist (First Communion). We wait until people (children and adults) understand that what they are receiving is not simply bread and wine, but the Body and Blood of Jesus Christ, changed by God, changed from bread and wine to the substance that then changes us to be more like Christ. First Communion is a special time for the whole family, who celebrates with the one who is receiving for the very first time, and we recall our own First Communion. As we continue to receive the Lord, we ask him to continue to “change our hearts”.