124 But, on the contrary, the very nature of the sacrament demands that its reception should produce rich fruits of Christian sanctity. Admittedly the congregation has been officially dismissed, but each individual, since he is united with Christ, should not interrupt the hymn of praise in his own soul, "always returning thanks for all in the name of our Lord Jesus Christ to God the Father." The sacred liturgy of the Mass also exhorts us to do this when it bids us pray in these words, "Grant, we beseech thee, that we may always continue to offer thanks . . . and may never cease from praising thee." Wherefore, if there is no time when we must not offer God thanks, and if we must never cease from praising Him, who would dare to reprehend or find fault with the Church, because she advises her priests and faithful to converse with the divine Redeemer for at least a short while after holy communion, and inserts in her liturgical books, fitting prayers, enriched with indulgences, by which the sacred ministers may make suitable preparation before Mass and holy communion or may return thanks afterwards? So far is the sacred liturgy from restricting the interior devotion of individual Christians, that it actually fosters and promotes it so that they may be rendered like to Jesus Christ and through Him be brought to the heavenly Father; wherefore this same discipline of the liturgy demands that whoever has partaken of the sacrifice of the altar should return fitting thanks to God. For it is the good pleasure of the divine Redeemer to hearken to us when we pray, to converse with us intimately and to offer us a refuge in His loving Heart.
Source: Mediator Dei (Vatican.va)