Moral imperative to decrease negative emotions
Wherein I argue that there is a moral obligation to minimize bad feelings within oneself.
Before I get started I want to make clear that minimizing bad feelings arising in oneself is not the same as suppressing said feelings when they arise. One should, for their own health, fully explore what one is feeling, let it to the surface and understand it as much as possible. My intention is not to get you to hide or suppress your feelings, but to challenge the idea that "all feelings are created equal" and/or give some clarity as to why things like anger management are good.
I'll leave the definition of what a 'bad feeling' is to the reader. I write this not for something to be imposed upon someone, but for someone who seeks goodness within their self; and thus purely subjective definitions are satisfactory. A biochemical approach would probably suffice (feelings marked by a lack of dopamine or serotonin, or feelings marked by an increase in catecholamines) but it's beyond even what I am willing to pretend to be an expert at.
For myself, I think of 'bad feelings' simply as those that I don't enjoy; or feelings that I associate with things I don't want in my life. Someone I love passes away: sadness. Bad feeling. Someone I thought was a good friend steals my money: anger. Bad feeling. Naked pictures of me go viral on the Internet and everyone makes fun of my tiny penis: humiliation. Bad feeling. I realllly want a Super Nintendo for Christmas but I get sewing machine instead: disappointment. Bad feeling.
Maybe you have your own different set; or maybe it's similar or the same as mine, but you never get angry so that's something you don't have to worry about; or maybe your parents got you the toy you wanted and you haven't yet felt disappointment. Whatever.
Here I will have to pretend a bit like I am an expert on something I am not; but generally emotion serves a variety of evolutionary purposes; and those purposes are better suited if emotion 'spreads' through a tribe or group. If I get scared of some legitimate threat; and we all run away together and survive; our genes are more likely to be passed on than if I get scared and run away but you hang out like everything is hunky-dory and get eaten by that Saber-toothed Velocirpator. Suffice to say, emotions spread. Our ability to empathize is 'older' than our ability to think abstract thoughts, evidenced by the super sweetness of a loving kitty that is never going to solve a differential equation. Reptiles can't empathize, mammals can. Humans can also think complex abstract thoughts and reason about the world in non-instinctual ways; and often we like to think that is actually how we go about functioning through the world.
But consider, before we were able to rotate a 3D object in our mind and make educated guesses about the squareroot of 1207, or use language and have the thought "that guy over there looks scared"; we (in a very broad mammalian sense) communicated with emotion. Fear, love (aka attachment), jealousy, anger, sadness. Maybe some clicks or chirps or yells, but generally emotion is spreading from one of us to the other in a way beyond our immediate control.
As an extreme mental exercise, imagine you are contentedly watching your favorite TV show, or reading a nice novel, or having a delicious bowl of something-or-other. Suddenly your spouse walks in and starts throwing a temper tantrum. They are pissed off. They start yelling at you; nothing specific just that they are mad and it's your fault. Are you content anymore? Did you have some thought, "hrmmm analyzing this situation it appears that my emotional state should reflect one more similar to my partner, let me down regulate my dopamine and increase catecholamines in my brain; ah I feel like shit, that's better?"
NO! Something more primitive than your prefrontal cortex did all of this without your permission; and unless you are on the autistic spectrum, a really advanced meditator, or perhaps sociopath; your emotional state is going to be strongly influenced by those around you. When air vibrates at ~261 hertz you hear middle-c and when others around you are angry or sad you feel it.
This is where I want to stop writing and say, yep see, I made my point. But that doesn't always go over well so I will be a bit more explicit.
We have seen through simple examples that we define our own bad feelings simply as the emotion associated with things you don't want to happen; and juxtaposing the feelings you have when things are going more or less your way. There is a biochemical reason for your not enjoying anger, and enjoying feeling love; but what it all comes down to is that some feelings are enjoyable and some are not.
We have also seen that emotion in all its forms spreads from person to person; evidenced by it being the entire evolutionary purpose of emotion; to communicate internal states to those around you.
In the same way a person striving toward morality cannot in good conscious steal from a needy person because they understand that the damage they cause the needy person, and it conflicts with their morals; I posit that a moral person must take steps to decrease the arising of negative emotion in their self because they understand that these unfavorable emotions are spreading willy-nilly to those around them.