This homily by Patriarch Bartholomew, Patriarch of Constantiniple, given in the presence is His Holiness, Pope Benedict XVI, includes some very good reflections on the sacred liturgy:
"Every celebration of the Divine Liturgy is a powerful and inspiring con-celebration of heaven and of history. Every Divine Liturgy is both an anamnesis of the past and an anticipation of the Kingdom. We are convinced that during this Divine Liturgy, we have once again been transferred spiritually in three directions: toward the kingdom of heaven where the angels celebrate; toward the celebration of the liturgy through the centuries; and toward the heavenly kingdom to come.
"This overwhelming continuity with heaven as well as with history means that the Orthodox liturgy is the mystical experience and profound conviction that "Christ is and ever shall be in our midst!" For in Christ, there is a deep connection between past, present, and future. In this way, the liturgy is more than merely the recollection of Christ's words and acts. It is the realization of the very presence of Christ Himself, who has promised to be wherever two or three are gathered in His name.
"At the same time, we recognize that the rule of prayer is the rule of faith (lex orandi lex credendi), that the doctrines of the Person of Christ and of the Holy Trinity have left an indelible mark on the liturgy, which comprises one of the undefined doctrines, "revealed to us in mystery," of which St. Basil the Great so eloquently spoke. This is why, in liturgy, we are reminded of the need to reach unity in faith as well as in prayer. Therefore, we kneel in humility and repentance before the living God and our Lord Jesus Christ, whose precious Name we bear and yet at the same time whose seamless garment we have divided. We confess in sorrow that we are not yet able to celebrate the holy sacraments in unity. And we pray that the day may come when this sacramental unity will be realized in its fullness."
The Patriarch continues later on:
"Thus our worship coincides with the same joyous worship in heaven and throughout history. Indeed, as St. John Chrysostom himself affirms: "Those in heaven and those on earth form a single festival, a shared thanksgiving, one choir" (PG 56.97). Heaven and earth offer one prayer, one feast, one doxology. The Divine Liturgy is at once the heavenly kingdom and our home, "a new heaven and a new earth" (Rev. 21.1), the ground and center where all things find their true meaning. The Liturgy teaches us to broaden our horizon and vision, to speak the language of love and communion, but also to learn that we must be with one another in spite of our differences and even divisions. In its spacious embrace, it includes the whole world, the communion of saints, and all of God's creation. The entire universe becomes "a cosmic liturgy", to recall the teaching of St. Maximus the Confessor. This kind of Liturgy can never grow old or outdated."