Why do people forgive the guy who burned their house down, but still hate that one relative who had a nasty tone while thanking them for a birthday present? Here's why we nurse grudges about small things, but forgive the big ones.
We seem to have a kind of pettiness built into our nature. We will watch soppy movies about the redemption of murderers, or long tv series about gleeful serial killers, but have a character in a movie litter and we want them in prison. Our real lives are not exempt from this. We can nurse a grudge against someone who gave us a dirty look for years. When someone we love screams at us, we forgive them in a few days.
A team of scientists from UCLA, Harvard, and the University of Virginia conducted a series of experiments that showed the people are bad at predicting how hurt will affect them over time. We tend to assume the more painful injuries, the major ones, or the ones committed by loved ones, will cause the most pain over time. In a preliminary study, the team had people rate how they thought they would feel both when a series of unpleasant things happened to them, and a week afterwards. The series included everything from being turned down for a date, to a restaurant refusing use of the bathroom because they weren't paying customers, to a close friend becoming a neo-Nazi. The participants in the study believed that, if they disliked something or someone intensely at the moment of injury, they would still dislike them strongly (if not as strongly), a week later. Minor offences would also incur dislike, but less dislike at the time, and also less dislike a week later. Obviously, the scientists couldn't check the participants predictions - although if they tried it would either be a cruel experiment or an inspired piece of performance art. So they went on to another series of experiments.
The next group of participants had a little project to do. They would write an autobiographical story, then switch stories with another participant, and assess each other's personalities based on the story. At different times during the experiment, they would receive sheets asking them to write down how they did feel about that partner, and how they thought they soon would feel about that partner. Partner is a bit of a strong word, though. Half the time, the participants would actually meet up with the partner afterwards, and discuss their stories and profiles. Half the time, they would never see or speak to the partner again - during these times the other person was referred to as the "nonpartner."
Right away, there was trouble. When the participants met with their partners, or nonpartners, the other person insulted them. This was not good news, especially for those who had to meet with the disagreeable person again. The participants were asked how they felt about the other person, and the responses were not positive. They were asked how they would feel about the other person. Again, the responses were not positive. Then, after about five minutes, they were asked how they did feel about the other person. The nonpartnered group still hated the person they soon would have to give their stories to, but who they wouldn't have to meet again. The partnered group, however, suddenly started to feel forgiving. In a variation of the experiment, the two different participants were in a room and the future "partner" insulted one of them. The insulted person felt far more kindly towards the partner than the witness did.
Why do we furiously resent the minor insults but forgive, or at least let go, of the major ones? Why do we let those close to us insult us in ways we'd never take from a stranger? According to the study authors, it's because we can afford to.
If the hurt is minor, we can let it fester. If the pain is major, we find ways to calm ourselves down. We do similar things when we are physically injured. A gunshot wound can cause us less overall pain than a bad back, because we go to the hospital when we're shot, while we're perfectly content to wait for weeks before we seek treatment for a bad back. The study authors point out that we make the same calculation when we travel. A trip to Costa Rica and a trip to San Diego take the same time, for me, because I'll drive to San Diego but I'll fly to Costa Rica. When something becomes too much trouble, or too painful, for us to put up with it, we take steps to alleviate the pain. This happens both physically and mentally. If holding a grudge means we have to be angry and miserable for a long time, we find a way to stop being angry. If we just suffer a little annoyance, we allow it. Or sometimes we even enjoy it.