This is new content in the second edition of Praying the Mass: The Prayers of the People, from Chapter 1, "Preparing for Prayer".
At the Second Vatican Council, the Church confirmed five times that the Eucharistic liturgy is both the source and summit of the activity of the Church, and therefore of each of her members:
[T]he liturgy is the summit toward which the activity of the Church is directed; at the same time it is the font from which all her power flows. (CSL 10)
Taking part in the Eucharistic sacrifice, which is the fount and apex of the whole Christian life, they offer the Divine Victim to God, and offer themselves along with It. (Lumen Gentium 11)
[P]astors should see to it that the celebration of the Eucharistic Sacrifice is the center and culmination of the whole life of the Christian community. (Christus Dominus 30.2)
[T]he Eucharist shows itself as the source and the apex of the whole work of preaching the Gospel. (Presbyterorum Ordinis 5)
By the preaching of the word and by the celebration of the sacraments, the center and summit of which is the most holy Eucharist, He brings about the presence of Christ, the author of salvation. (Ad Gentes 9)
The Eucharist is the ultimate aim (but not the only aim) of life in Christ: communion with God and His Church in Holy Communion. It is also the primary source (but not the only source) of that Christian life. During the years following Vatican II, there seems to have been a misconception that going to Mass once a week was all a Catholic should need. But the Council said exactly the opposite, that although the Eucharist is the source and summit, the spiritual life
is not limited solely to participation in the liturgy. The Christian is indeed called to pray with his brethren, but he must also enter into his chamber to pray to the Father, in secret; yet more, according to the teaching of the Apostle [Paul], he should pray without ceasing. We learn from the same Apostle that we must always bear about in our body the dying of Jesus, so that the life also of Jesus may be made manifest in our bodily frame. (CSL 12)
That quote from the Constitution on the Liturgy was referring to your personal prayer life. Another document from the Council relates those same aspects of the spiritual life to the laity:
[The laity] should all remember that they can reach all men and contribute to the salvation of the whole world by public worship and prayer as well as by penance and voluntary acceptance of the labors and hardships of life whereby they become like the suffering Christ. (Apostolicam Actuositatem 16)
Devout participation in the Mass gives life to your personal prayer, and by nurturing your prayer life, your participation in the Mass becomes deeper and more fruitful. A deeply personal life of prayer is the key to an immensely fruitful life of faith. The Church describes the necessity of an intimate relationship with Christ in these words from Vatican II:
[T]he success of the lay apostolate depends upon the laity’s living union with Christ, in keeping with the Lord’s words, “He who abides in me, and I in him, bears much fruit, for without me you can do nothing” (John 15:5). This life of intimate union with Christ in the Church is nourished by spiritual aids which are common to all the faithful, especially active participation in the sacred liturgy. … In this way the laity must make progress in holiness in a happy and ready spirit, trying prudently and patiently to overcome difficulties. (Apostolicam Actuositatem 4)
If you don’t have a “life of intimate union with Christ,” then the seed of the Eucharist ends up on “the path” or on “rocky ground” where it will not bear fruit. (Matt. 13:4-5) Prayer is the door to that union with Christ; it is “the raising of one’s mind and heart to God.” (Catechism 2559)
The liturgy (and in particular the Mass) is the “corporate” worship of the Church. The word “corporate” might make you think of businesses and companies and corporations, but it comes from the Latin corporare which means “to form into a body.” The word means “pertaining to a body,” and since the Church is the Body of Christ (of which you are a member), it makes sense that the public, official worship of the Church is her corporate worship.
Just as when engaging in full-body exercise, you need to warm up by stretching individual muscle groups, each member of the Body of Christ needs to engage in a similar discipline to prepare for corporate prayer: “warming up” with personal prayer. This can be done at home or at your church, although you can pray anywhere, anytime. Prayer can be vocal, meditative, or contemplative. (cf. Catechism 2720-2724) The Church also recommends devotional prayer, such as the Stations of the Cross, the Rosary, the Chaplet of Divine Mercy, and novenas and litanies. A most excellent form of prayer is Eucharistic Adoration, time spent in prayer in the presence of the Blessed Sacrament either reserved in the tabernacle or exposed in a monstrance. The Church encourages these devotional forms of prayer because they harmonize with the liturgical seasons, are shaped by the liturgy, and lead us back to the liturgy itself. (cf. CSL 13)
However and whatever and wherever you pray, just pray! Build a habit of daily prayer. If you don’t warm up before exercising, your body will not react properly (and you might injure yourself). If you don’t “warm up” before the prayer of the Mass, you might find yourself too easily distracted by things going on around you. If you find that your mind often wanders during Mass, you may want to pray before Mass for greater concentration. Consider praying to your guardian angel for assistance: because the Mass is a participation in the heavenly liturgy, all the angels of Heaven, including your guardian angel, are present at every celebration of the Eucharist. Ask your angel to help you stay focused on the spiritual realities present at the Mass, especially the mystery of faith, the miraculous change of the bread and wine into the Eucharist.