Two Sacraments of Service to Others (1533-1535)
The initiation sacraments (Baptism, Confirmation, and Eucharist) call the believer to holiness and confer the graces needed for our pilgrimage. Holy Orders and Matrimony (although contributing to the person’s salvation) are directed primarily to the salvation of others.
A Sacrament gives grace of and by itself, by its own power. This is because Jesus attached grace to the outward sign, so to speak, so that that outward sign and grace always go together.
But our own attitude does matter. Our interior dispositions have an effect on the amount of grace we receive. The more perfect is our sorrow in the sacrament of Reconciliation, the more ardent our love in receiving the Holy Eucharist, the more lively our faith in receiving Confirmation—then the greater will be the grace we receive. Our dispositions do not cause the grace; they simply remove the obstacles to the freer flow of grace and, in a sense, make more room for grace.
We can, of course, by a positive act of the will prevent the grace of the Sacrament from entering our soul: for example, by positively not wanting to receive it or by not being truly repentant for mortal sin. (Adapted from Catholic City)