Vatican Council II expressed the purpose of the sacraments
and the relationship between Christ acting and the reception
of the sacraments.
Constitution On the Sacred Liturgy, 59
"The purpose of the sacraments is to sanctify, to build up the
Body of Christ and, finally, to worship God. Because they are
signs, they also instruct. They not only presuppose faith, but
by words and objects they also nourish, strengthen, and
express it."
Constitution On the Sacred Liturgy, 7
"He (Jesus) is present in the sacraments by his power, in such
a way that when someone baptizes, Jesus himself baptizes. "