As we in the United States approach Thanksgiving, we should cultivate in our souls the virtue of gratitude. To this end, I recommend these words from St. Thomas Aquinas (1225-1274), excerpted from the Summa Theologiae (II.Q106):
Thanksgiving [gratiarum actio] in the recipient corresponds to the favor [gratia] of the giver: so that when there is greater favor on the part of the giver, greater thanks are due on the part of the recipient. Now a favor is something bestowed “gratis”: wherefore on the part of the giver the favor may be greater on two counts. First, owing to the quantity of the thing given: and in this way the innocent owes greater thanksgiving, because he receives a greater gift from God, also, absolutely speaking, a more continuous gift, other things being equal. Secondly, a favor may be said to be greater, because it is given more gratuitously; and in this sense the penitent is more bound to give thanks than the innocent, because what he receives from God is more gratuitously given: since, whereas he was deserving of punishment, he has received grace. Wherefore, although the gift bestowed on the innocent is, considered absolutely, greater, yet the gift bestowed on the penitent is greater in relation to him: even as a small gift bestowed on a poor man is greater to him than a great gift is to a rich man. And since actions are about singulars, in matters of action, we have to take note of what is such here and now, rather than of what is such absolutely, as the Philosopher observes (Ethic. iii) in treating of the voluntary and the involuntary….
As stated above (Article 5), gratitude regards the favor received according the intention of the benefactor; who seems be deserving of praise, chiefly for having conferred the favor gratis without being bound to do so. Wherefore the beneficiary is under a moral obligation to bestow something gratis in return. Now he does not seem to bestow something gratis, unless he exceeds the quantity of the favor received: because so long as he repays less or an equivalent, he would seem to do nothing gratis, but only to return what he has received. Therefore gratitude always inclines, as far as possible, to pay back something more.