'Created grace' is not meant to signify that grace is a creature. It is meant to signify that grace exists in humans as accident rather than as essence, which is just saying that humans don't have grace by their nature but that it has to be granted by God. To quote Aquinas:
So, why not call it "accidental grace" instead of the misleading "created grace"?
Because the Latin world habitas
[that is translated rather poorly in some ways] has connotations of effect
with respect to the gift of grace more than it does of the grace itself.
It is the idea that sanctifying graces change the person. A better ideational representation might be to call it transfiguring
grace, or re-creational grace, though the latter one has its problems.
with reference to the virtues, for example, results in ideas of such things as infused virtue.
Let's say I cuss: Every time I split my finger open with the hammer I say "BLAST IT!!" or some form thereof...Well "BLAST IT" is not a particularly good thing for a contemplative hermit to be shouting around in the skete with all the windows open for the neighbors to hear, and not only is it bad example, it is disquieting to the soul.
So for months and years, I work, by dint of prayer and grace, every day to try to stop hollering "BLAST IT" every time something hurts or I get frustrated. Well...The working and praying pays off and I am down to 5 "BLAST ITs" per week rather than 49 of them.
But that is not really good enough for sanctity and I have asked God to sanctify my life.
Eventually, one day, I stand at the kitchen window and realize that I have not said "BLAST IT" for months and months. My response is not to pat myself on the back for all the hard work; My response is to get on my knees and thank God for answering my prayer for removing that habit from me entirely, something that I could not have done without his habitation in my soul...
Habitus is the way that I, as a human, can be indwelled by the Living God, the Trinity.
Well...there it is...an infused virtue of patience that has resulted in a considerably quieter neighborhood and interior space where prayer can now go much deeper on account of the custody of one of my greater passions.
You see?....that is what the Church has understood to be "created grace" since the time of St. Thomas and even before that....and what follows is a more scholarly discourse for your reading pleasure:
The following is from A Brief Catechesis on Nature and Grace (Ignatius Press, 1984):
The supernatural, one might say, is that divine element which man’s effort cannot reach (no self-divinization!) but which unites itself to man, “elevating” him as our classical theology used to put it, and as Vatican II still says (Lumen Gentium, 2), penetrating him in order to divinize him, and thus becoming as it were an attribute of the “new man” described by St. Paul. While it remains forever “un-naturalizable,” it profoundly penetrates the depths of man’s being. In short, it is what the old Scholastics and especially St. Thomas Aquinas called (using a word borrowed from Aristotle which has often been completely misunderstood) an accident, or call it a habitus, or “created grace”: these are all different ways of saying (even if one thinks they need various correctives or precisions) that man becomes in truth a sharer in the divine nature (divinae consortes naturae; 2 Pet 1:4). We do not need to conceive of it as a sort of entity separated from its Source, something like cooled lava — which man would appropriate to himself. On the contrary, we wish to affirm by these words that the influx of God’s Spirit does not remain external to man; that without any commingling of natures it really leaves its mark on our nature and becomes in us a principle of life. This Scholastic notion of created grace, so often belittled today, does express the incontrovertible fact that “it is we, ourselves, and our creaturely being, which the active presence in us of the Spirit makes divine, without for that reason absorbing us and annihilating us in God."
For St. Thomas, as Fr. Louis Bouyer explains,
[T]he soul…will find its completeness and go beyond itself in God. Disagreeing with Peter Lombard, in fact, he would not admit that grace is purely and simply the gift of the Holy Spirit, of the Third Person of the Trinity as it is in itself…. He realized that if such were indeed the case, man would certainly be the temple of the Spirit, but not God’s living temple, vivified by the presence of its Guest who assimilates our life to his divine life. The uncreated grace of the gift of the Spirit, according to him, has its prolongation in the soul itself in created grace, i.e., a divine quality that assimilates the soul to God and makes it share in his own life. (Introduction à la vie spirituelle, Paris: Desclée, 1960, 154-55)