Perhaps the experience varies for others. Within myself, I have come to realize the following.
The very phrase to “hold” a grudge, reveals that we, through our active effort, prevent the grudge from escaping. A certain pleasure, though not unmixed with pain is generated through the remembrance. Like the pleasure that arises from picking a sore tooth. I am convinced, that if the grudge produced no pleasure, or feeling of satisfaction, we would drop it before very long.
This feeling of satisfaction is also noticeable in ‘Moral Outrage’. Self righteousness. Compulsively thinking of resentment produces this as well.
So what is the nature of the pleasure? It seems to me, that there is more than one such sort.
The first, is a feeling of superiority. If I consider myself the ‘wronged’, or the ‘insulted’, then the other person has behaved wrongly, and I, by the very fact that I feel wronged, am righteous, have the right to condemn, and humiliate him.
The word humiliate is important here. Humiliation means guilt, submission, and acceptance of one’s wrongdoing. If the person who has wronged me does not accept, or feel guilty, my pleasure or satisfaction is lessened. It is as if I am feeding off the guilt of another person. The experienced observer will see that this is nothing but Sadism, under the guise of moral outrage.
Another symptom , is the unwillingness to let go. That I prefer to hate, and suffer all the discomfort (for hating is physically very uncomfortable – blood pressure, anxiety etc.), than to let go, and have peace.
This shows, that as this type of Sadist, I NEED the guilt of the other. Without it, I feel alone, insufficient, and insignificant. This means that my Sadism, in the first place is due to my inability to stand by myself. I fear aloneness.
“Love me or hate me, but don’t ignore me.” – Is the motto of a person in such a state. It is not my place to judge, but perhaps an alternative to such an unsatisfactory state of affairs, is to learn to love oneself, and trust oneself. To make one’s power proceed from inside rather than from outside.