St. Teresa de Jesus warns us against holding grudges.
“You will say that these are little things which have to do with human nature and are not worth troubling about; do not trifle with them, for in religious houses they spread like foam on water, and there is no small matter so extremely dangerous as are punctiliousness about honor and sensitiveness to insult. Do you know one reason, apart from many others, why this is so? It may have its root, perhaps, in some trivial slight — hardly anything, in fact — and the devil will then induce someone else to consider it important, so that she will think it a real charity to tell you about it and to ask how you can allow yourself to be insulted so; and she will pray that God may give you patience and that you may offer it to Him, for even a saint could not bear more. The devil is simply putting his deceitfulness into this other person’s mouth; and, though you yourself are quite ready to bear the slight, you are tempted to vainglory because you have not resisted something else as perfectly as you should.
This human nature of ours is so wretchedly weak that, even while we are telling ourselves that there is nothing for us to make a fuss about, we imagine we are doing something virtuous, and begin to feel sorry for ourselves, particularly when we see that other people are sorry for us too. In this way the soul begins to lose the occasions of merit which it had gained; it becomes weaker; and thus a door is opened to the devil by which he can enter on some other occasion with a temptation worse than the last. It may even happen that, when you yourself are prepared to suffer an insult, your sisters come and ask you if you are a beast of burden, and say you ought to be more sensitive about things. Oh, my sisters, for the love of God, never let charity move you to show pity for another in anything to do with these fancied insults, for that is like the pity shown to holy Job by his wife and friends.” (Ch. 12,
paras. 8 & 9).
“I often tell you, sisters, and now I want it to be set down in writing, not to forget that we in this house, and for that matter anyone who would be perfect, must flee a thousand leagues from such phrases as: “I had right on my side”; “They had no right to do this to me”; “The person who treated me like this was not right”. God deliver us from such a false idea of right as that! Do you think that it was right for our good Jesus to have to suffer so many insults, and that those who heaped them on Him were right, and that they had any right to do Him those wrongs? I do not know why anyone is in a convent who is willing to bear only the crosses that she has a perfect right to expect: such a person should return to the world, though even there such rights will not be safeguarded. Do you think you can ever possibly have to bear so much that you ought not to have to bear any more? How does right enter into the matter at all? I really do not know.” (Ch. 13, para. 1).