Liturgy is an "action" of the whole Christ (Christus totus). Those who even now celebrate it without signs are already in the heavenly liturgy, where celebration is wholly communion and feast. (CCC 1136).  

By virtue of our participation in Christ's work as members of His Mystical Body, we participate in the divine life of the Trinity, an eternal exchange of love between the Father and Son that is the Holy Spirit. This action – liturgical participation – is our right and duty by baptism (SC 14). As with any sacrament, the action or "doing" is all God's, but as a good parent, He invites us to join in it, both as the worship for which we are made and for the sanctification of the world.