Celebration and participation in a Holy Mass is not the same like participating in non-Catholic worship. At Holy Mass, the Christian community truly encounters Jesus Christ with whom we are called to nurture a living relationship of discipleship. The Holy Mass is a commemoration of Christ’s Passover. At every Mass, the one sacrifice of Christ offered once for all on the cross remains ever present and the work of our redemption is carried out. The Holy Mass is a sacrifice in the most real way because it re-presents (makes present) the sacrifice of the cross. (see CCC 1364-1366). Precisely so, we understand the Eucharist to be the Source and summit of Christian life.
The celebration of Mass is a corporate act, an act of the whole assembly gathered for worship. All the particular ministries serve this corporate function (GIRM, no. 27). In the Mass, the Church is joined to the action of Christ, the high point both of the action by which God sanctifies the world in Christ and of the worship that the human race offers to the Father, adoring him through Christ, the Son of God, in the Holy Spirit (no. 16). We are joined to this divine action through baptism, which incorporates us into the risen Christ. This action, which lies at the center of the whole Christian life (no. 16) is not initiated by us but by God acting in and through the Church as the body of the risen Christ. It becomes our action only to the extent that we give ourselves to this mystery of redemptive worship. The liturgy is designed to bring about in all those who make up the worshiping assembly a participation of the faithful both in body and mind, a participation burning with faithful, hope, and charity (no. 18). To the extent that we are able to participate in this way, the work of redemption becomes personally effective for each of us. By such participation, the General Instruction says, we make the actions and prayers of the liturgy our own; we enter more fully into our personal communion with Christ's redeeming act and perfect worship (see no. 54, 55, etc.). In the celebration of Mass the faithful are a holy people, a chosen people, a royal priesthood: they give thanks to God and offer the Victim not only through the hands of the priest but also together with him and learn to offer themselves. They should endeavor to make this clear by their deep sense of reverence for God and their charity toward brothers and sisters who share with them in the celebration (no. 95). They should become one body, whether by hearing the word of God, or joining in prayers and liturgical song, or above all by offering the sacrifice together and sharing together in the Lord's table (no. 96). Because the whole liturgy is a corporate act of the gathered assembly (GIRM no. 34; Catechism of the Catholic Church no. 1144), there are certain parts of the Mass that are to be done by the whole assembly, the congregation of the faithful and all the ministers, in order to express the corporate nature of this act. Through these actions, the entire congregation of the faithful joins itself to Christ in acknowledging the great things that God has done and in offering the sacrifice (no. 78).