There is an error in your OP (infinite amount) which is probably the cause of the confusion.
We do not receive an “infinite” amount of sanctifying grace.
Some quotes from Fundamentals of Catholic Dogma:
The degree of justifying grace is not identical in all the just. (De fide)
Grace can be increased by good works. (De fide)
…The Council of Trent, however, declared that the measure of the grace of justification received varies in the individual person who is justified, according to the measure of God’s free distribution, and to the disposition and the co-operation of the recipient himself. D 799
S. Scripture teaches us that the measure of the grace bestowed on each individual just person varies. Eph. 4:7: “But to every one of us is given grace, according to the measure of the giving of Christ.” 1 Cor. 12:11: “But all these things, one and the same Spirit worketh, dividing to every one according as he will.” In S. Scripture we read also of an increase of grace. 2 Peter 3:18: “Grow in grace.” Rev. 22:11: “He that is just let him be justified still.”