Thomas Aquinas

“ Extreme Unction, for this very reason, is given the last place among those sacraments which are ordained to the perfection of the individual.
Art. 3 - Whether the Eucharist is the greatest of the sacraments? Objection 1: It seems that the Eucharist is not the principal of the sacraments. For the common good is of more account than the good of the individual (1 Ethic. ii) . But Matrimony is ordained to the common good of the human race by means of generation: whereas the sacrament of the Eucharist is ordained to the private good of the recipient. ”

“ We may likewise gather the number of the sacraments from their being instituted as a remedy against the defect caused by sin. For Baptism is intended as a remedy against the absence of spiritual life; Confirmation, against the infirmity of soul found in those of recent birth; the Eucharist, against the soul's proneness to sin; Penance, against actual sin committed after baptism; Extreme Unction, against the remainders of sins---of those sins, namely, which are not sufficiently removed by Penance, whether through negligence or through ignorance; order, against divisions in the community ”

“ Although contempt of any of the sacraments is a hindrance to salvation, yet it does not amount to contempt of the sacrament, if anyone does not trouble to receive a sacrament that is not necessary for salvation. ”