Thomas Aquinas

“ Therefore there can be superstition by reason of excess even in the worship of God.
I answer that, A thing is said to be in excess in two ways. First, with regard to absolute quantity, and in this way there cannot be excess in the worship of God, because whatever man does is less than he owes God. Secondly, a thing is in excess with regard to quantity of proportion, through not being proportionate to its end. Now the end of divine worship is that man may give glory to God, and submit to Him in mind and body. ”

“ In the second place, falsehood in outward worship occurs on the part of the worshiper, and especially in common worship which is offered by ministers impersonating the whole Church. For even as he would be guilty of falsehood who would, in the name of another person, proffer things that are not committed to him, so too does a man incur the guilt of falsehood who, on the part of the Church, gives worship to God contrary to the manner established by the Church or divine authority, and according to ecclesiastical custom. ”

“ Consequently, whatever a man may do conducing to God's glory, and subjecting his mind to God, and his body, too, by a moderate curbing of the concupiscences, is not excessive in the divine worship, provided it be in accordance with the commandments of God and of the Church, and in keeping with the customs of those among whom he lives. ”