Why do we concern ourselves with conflict and plotting? That man you are angry with – can you wish for him anything worse than death? He is going to die without your doing a thing.

Seneca, On Anger

Agnes Callard has an argument for why you can be angry forever. I think it’s wrong, but it useful for thinking about the nature of emotions:

1. There are reasons to be angry
2. Reasons to be angry do not go away.
3. If reasons to be angry do not go away, then all things considered, you have reasons to remain angry forever.
4. Therefore, all things considered, you have reasons to be angry forever.

Callard calls this the argument from grudges:

Once you have a reason to be angry, you have a reason to be angry forever.

Many people accept (1). (2) is more surprising. Here’s Callard on the intuition:

The tendency to cling to anger through apologies and recompense, for years sometimes and to the detriment of all parties concerned, is routinely dismissed as irrational...

But this idea ignores the fact that there are reasons to remain angry. And the reasons are not hard to find: they are the same reasons as the reasons to get angry in the first place. Apologies, restitution, and all the rest do nothing to cancel or alter the fact that I stole, nor the fact that I ought not to have stolen.

In other words, reasons to be angry do not go away. If you’re angry at the fact that someone stole from you, the act that they stole does not go away.

Grudges are not that different from other emotions, like gratitude and grief. If you’re grateful that someone helped you in a time of need, then the fact that they helped you in a time of need is something you can be grateful about forever. If you experience grief at the death of a loved one, then you have a reason to grieve for all time.

This comparison highlights an asymmetry between positive and negative emotions. It’s reasonable to be grateful forever, but not to hold grudges or grieve forever.

This asymmetry seems fundamentally right to me.

Emotions are instrumentally useful. They shape our experiences, actions, and model of the world. When we have a reason to be angry, it’s not just because someone stole from us. It’s because being angry will help us stand up for our rights. In my view, by responding in a  particular way, your reasons are dominated by your past, what you’d like to do and who you want to be. Callard’s view assumes that the reasons to have some emotional response are merely determined by the facts we are reacting to. The problem with this view is that it's not clear what would determine what makes some emotions fit to a situation other than facts about us, our needs and past, and the situation.

This explains why anger fades overtime. Emotion fades as it becomes useful. There is no point at being angry at someone when doing so will make no difference. It also explains the asymmetry between positive and negative emotions. Prompting positive emotions by remembering reasons to be grateful or happy is often useful for crafting who we want to be and how we want to act.

Anger is only useful when it’s useful, and for most of us, that’s increasingly rare.