A - Thanks for the question. Just a side-note - previous posts on the Eucharist, which can be found here, here and here are from the same person asking the question above. You can tell someone has been deeply thinking about the Eucharist and I encourage all of us to follow in this person's footsteps. Good thoughts!
First of all, it is impossible for God to give differing amounts of grace. The reason is that grace is an unmerited gift of the inner life of God. God cannot give just a part of himself, but the fullness of His love. Now, while in this world we will be at a place in life to make efficacious (effective) a certain "amount" of this grace dependent upon ourselves.
An example I was given by one of my graduate school profs might help.
God's grace could be compared to an infinite Niagara Falls. We are each a container that is put under the waterfall to capture some of this grace. For instance, St. Francis might be a tanker truck that pulls up to the waterfall and is immediately filled. On the other hand, I am like a thimble that might get filled up, but doesn't have the spiritual capability of accepting the same amount of grace as St. Francis.
That is a good way of looking at the grace we receive in the Sacraments. If we are disposed to receive them, in other words there isn't something to keep us from validly receiving the Sacrament, then grace will come to us. As the Catechism says in 1127:
Celebrated worthily in faith, the sacraments confer the grace that they signify.But, from there it is up to us to use this grace. CCC, 1128 affirms what was said in 1127 and then tells us that we play a part as well.
This is the meaning of the Church's affirmation that the sacraments act ex opere operato (literally: "by the very fact of the action's being performed"), i.e., by virtue of the saving work of Christ, accomplished once for all. It follows that "the sacrament is not wrought by the righteousness of either the celebrant or the recipient, but by the power of God." From the moment that a sacrament is celebrated in accordance with the intention of the Church, the power of Christ and his Spirit acts in and through it, independently of the personal holiness of the minister. Nevertheless, the fruits of the sacraments also depend on the disposition of the one who receives them.Keep up the deep thinking!