1. To answer this question, it is necessary to recall what liturgy is. The sacred liturgy of the Catholic Church is her worship of God. Prayer is an integral part of worship but not the whole of it. Worship adds to prayer behavior appropriate to complete—at least symbolically—the interpersonal communing of prayer. For example, the Mass is a prayer completed by the offering of gifts and receiving of the Eucharist.
In the Mass, the behavior which completes prayer is more than symbolic; the communing of prayer is really perfected by the sacrifice and sacrament of the Eucharist. Just as marital love goes beyond the communing of conversation into the behavior by which love is made, so worship of God goes beyond the communing of prayer into the behavior by which the relationship with God is really accepted and developed. Now, any true lovemaking is preceded, accompanied, and followed by loving thoughts and words; similarly, all true worship is preceded, accompanied, and followed by prayer. Indeed, prayer is so essential and determinative of acts of worship that worship can be considered prayer in action.
2. Members of the Church can worship apart from the liturgy, individually or in groups, but then their acts of worship, as excellent as they may be, constitute worship in the Church rather than worship by the Church. For example, when the faithful carry out a devotional exercise such as the stations of the cross, they are engaged in true worship in the Church, but this act of worship is nonliturgical and does not constitute the worship of the church.
3. Pius XII, in his great encyclical on the liturgy, Mediator Dei, explains that the Church acts in union with Jesus, who remains present to her in many ways, in particular when she offers prayers of praise and petition through him to our heavenly Father. He concludes with this clear statement of what the liturgy is: “The sacred liturgy is, consequently, the public worship which our Redeemer as Head of the Church renders to the Father, as well as the worship which the community of the faithful renders to its Founder, and through him to the heavenly Father. It is, in short, the worship rendered by the Mystical Body of Christ in the entirety of its Head and members.”10 Vatican II assumes this formulation into its own more complex teaching, which equally emphasizes liturgy’s aspects as worship and as redeeming and sanctifying act. In both aspects, the liturgy is primarily Jesus’ action, and he is always present in it (see SC 7).
4. The human life of the Incarnate Word is both a revelatory sign and an appropriate human response to revelation (21‑F). These two aspects mutually include one another, without becoming in any way confused. By the Incarnation, furthermore, the work of redemption, which is God’s work, also has been made human work, and thus a divine-human cooperation. Jesus consummated his human part of the work by his freely accepted death on the cross (see Jn 19.30), but his entire life expressed the commitment which led to this final act and prepared for it. Thus his whole life must be considered part of his redemptive act. This act, considered both as revelatory sign of God’s love and as human response to it, is made present to us in the Church’s liturgy, especially and centrally in the sacrifice and sacrament of the Eucharist (see SC 10; S.t., 3, q. 62, a. 5; q. 83, a. 1).
5. As a revelatory sign, the redemptive act presented in the liturgy is sacrament; it does what it signifies, because God’s revelation is really effective communication of himself to us. As a human response to God’s love, the redemptive sacrifice in which we participate in the liturgy is perfect worship, as Pius XII stresses. In the Spirit we are united with Jesus, the head of the Church, and through him we worship the Father.
6. In conclusion, there are two reasons why the liturgy ought to be the center of each Christian’s prayer life. First, in its essentials the liturgy is not created by the Church, but prescribed for the Church by Christ. By instituting the sacraments, Jesus provides his Church with God-given worship. Humility accepts what God gives, and humility is the primary characteristic of Christian prayer. The liturgy should therefore be accepted humbly as the principle of any effort of personal prayer.
7. There is, however, a second and more basic consideration. The whole of Christian life is to be lived in communion with Jesus. Liturgical worship is Jesus’ redemptive act made present for us to participate in, both as beneficiaries and as subordinated coredeemers of ourselves and others. Therefore, the prayer which is to form the remainder of one’s life must flow from and return to the liturgy as to its vital center, and in particular from and to the Eucharist as to its heart.
The liturgy, because it is the work of the whole Church, must have and does have a formal character, which some who dislike it call “objective” and “impersonal.” They mistakenly regard this quality as a defect, which they attempt to remedy either by “personalizing” the liturgy or by promoting other forms of prayer and devotion in place of it. However, the formality of the liturgy is no defect. Rather, this very quality is one of its important strengths, for in virtue of it the liturgy unites the whole Church with Jesus in a single harmonious choir together performing the same worship. To accept the demands of the liturgy upon oneself is to adapt oneself to life in the Spirit, to submit one’s subjectivity to communion in Jesus. This acceptance itself is an important act of humility and obedience—the virtues which are basic modes of Christian response.
Therefore, if we find ourselves insincere in doing the liturgy, if we miss in liturgical prayer the gratification of authentic self-expression, the remedy is not to tamper with the liturgy, but to change ourselves until we conform to the liturgy. We should not conform our voices to our minds, but rather our minds to our voices, as St. Benedict says (see SC 90). If one’s personal life is not lived in a Christian way, the liturgy itself becomes isolated and loses its essential point—namely, to be the medium by which we participate in redemption both passively and actively. If the liturgy is isolated, it quickly falls either into sterile formalism, coldly going through meaningless motions, or into fruitless emotionalism, which provides nothing but the apparent good of religion, stopping with the experience instead of proceeding to the whole reality of cooperation with God.
10. Pius XII, Mediator Dei, 39 AAS (1947) 528–29; The Papal Encyclicals, 233.20.