First, don’t tell me that the answer is just to “not bottle things up”, because that’s objectively incorrect too.

Well, no, it's not objectively incorrect. I get the sense that the main problem you have is communicating negative emotions without being overly confrontational or acerbic about it. My experience is that it's very possible to tell someone you're unhappy about something without making a major deal out of it.

Also, I'm curious about how often you find yourself in the situation we're taking about. Everybody had occasions where they have to vent frustrating, but if that's a super frequency occurrence, there might be something else going on. Sometimes it should be enough to take a deep breath, recognize that the issue is minor, and let it go.

This reminds me of something a European told me about dating in the US. "Americans say nothing is wrong and then blow up when it's a level 11 problem and i had no idea anything was wrong. Where I'm from we address it when it's a level 2 problem."

Be a level 2 problem, not a level 11 problem. That means you gotta fucking talk.

don't tell me that the answer is just to "not bottle things up"

I hate to be that guy, and believe me I was in that boat once. But the solution is to not reach the point where you are exploding from the amount bottled up.

Humans are not meant to be stoic creatures. People have feelings, that's called being human. You need to find someone you can trust(NOT A COWORKER), and every once and awhile vent to them about things that you aren't able to resolve with the person that's causing the frustration. That's your best solution.

Reading your replies, this seems to be more a super toxic work environment issue which I think if you fix, will resolve most of your issues. Due to this, I recommend ON-TOP of the previous recommendation, also either contacting HR about it, or if you do not feel comfortable with doing that, finding another job. You should not be being bullied by anyone let alone a manager. There are so many work policies in place in most work environments protecting you against this, and not to mention most civilized countries have laws against it.

Being said, if you feel that it is less of a you bottle things up, and more of a you aren't thick skinned enough to be able to handle the every day work-life without having anger issues and exploding, you may also want to look into some form of Anger management or calming technique. But honestly, it sounds like it's a combination of the first two issues and less of an anger issue.

It's corny and is championed by some shit heads but Meditations by Marcus Aurelius helped me to figure out how mentally center myself during tribulations.

Link to Internet Archive

1. You need to voice your concerns when they actually come up. The idea that showing emotions is objectively bad is completely false.
2. You need to learn how to phrase negative comments with a neutral tone. You should not be describing anyone as mean, rude, bitch. Especially not your coworkers. Do you mean straightforward? Concerned? Talkative? Direct? Extroverted? Confident?

First, don't tell me that the answer is just to "not bottle things up", because that's objectively incorrect too. Society doesn't want you to have any negative emotions.

I'm guessing you're a man. Society imposes this upon men in particular.

Tell society to fuck off. Have emotions, experience emotions, and process them like a human being.

Then take it a step further, and learn how to handle them like an emotionally intelligent human being.

I need to know how to not express negative emotions at all whatsoever unless I'm alone.

This is part of the problem. This is not what you need to know. You need to know how to express negative emotions without losing control of yourself or your reaction to your emotions.

I know it can be done because it is done in many other people on the planet.

People bottling things up and exploding when in a safe space is part of the problem.

I'll echo the idea of anger management, or even therapy in general.

Nobody who is healthy hides away their emotions. You're not alone in feeling the way you do. Society is sending you signals that you need to do something unhealthy, but that won't actually fix the problem.

This is a question for a therapist. So my answer is, whenever you have an open mind to the idea of being uncomfortable in order to grow, start researching therapists.

One of the most healthy practices you can do is to fully experience negative emotion, let it wash over you and fully occupy you, then breathe deeply and let that emotion go. Holding on to negative emotion has long term health consequences. Remember that you have no control over the world, just your own reactions to the world. I have a lot of anger that I try to let go of this way. Life has become a long series of just being shit on by everyone and everything. But what can I really do about it? Keep working and moving up the ladder to where the shit sandwiches have more bread I guess. In the meantime, I try to practice mindfulness with my emotions and breathe through them. You can use the Dune Litany Against Fear with pretty much any negative emotion.

So you harbor resentment.

Clear the air, don't take things personally, realize other people's emotions are out of your control and move on with life.

Easier said than done, though.

I think it’s more of finding ways to express negative emotions in a healthier/safer way, and not necessarily just suppressing it.

I recently took an anger management class. That might be a good place to start for you. One of the takeaways I got was that it's ok to have anger, but you need to learn and use different techniques for managing it.

Got to therapy. Seriously

Society doesn’t want you to have any negative emotions. I need to know how to not express negative emotions at all whatsoever unless I’m alone.

What about your friends or family? Particularly in some countries, it's true that public displays of unhappiness are taboo. Less-than-totally-public displays are kind of a huge part of people's social lives everywhere.

What is this 'society' nonsense? You can express your desires and feelings without having to explode, that's the solution. And when you eventually do, because you're human and mistakes will happen, apologise profusely and understand "the work" is not yet done. Also whatever you propose is not only a denial of your own humanity, in vain and for your own detriment (and immature too, which is not a good look!), but also the kind of things dudes try before they shoot up churches and festivals.

You are human, after all, a social animal. You're gonna have to open up as calmly as you can when the situation calls for it, instead of not saying anything because you don't feel brave enough to be vulnerable (maybe you feel like the people around you will only misunderstand you and make it worse?), so resentment doesn't add up in the background and you don't end up exploding. And I'm not just preaching here, I'm speaking from experience!

I would say therapy and find a healthy way to offload steam such as exercise or meditation or walking your dog or hitting a few balls at the driving range...etc you get the idea.

Regarding therapy, if you want to explore that it may take a few tries to find someone you click with but I have many friends who swear by it and say it was one of the best things they have done.

I would suggest that you try to process those swallowed emotions at a later time. Ask yourself why these things bother you, can you let them go, do you need an outlet to relieve them. Maybe you can relieve that pressure before you blow.

Some dark humor helps.

You have to do something physical. Run, do some intense workout with cardio and weights, wail on a punching bag. Maybe all 3.

Let your brain focus on something that isn't words in your head, and exhaust you physically, and you'll quickly learn how inconsequential other people's petty BS really is in the grand scheme of things.

The trick is having people with whom it is safe to voice negative thoughts and opinions. Generally it's the same people who confide in you. There are also other ways to vent that pressure a little bit in the short term, but expressing that negativity to other people is not really replacable.

For guys (as I assume you are), this can be very hard to find, or to build these kinds of relationships for cultural reasons, but it is fundamentally necessary to being an emotionally healthy person.

You voice the small negatives on an ongoing basis so they don't pile up to the point that they're explosive.

Getting a therapist, so you have someone you're paying to hear your negative thoughts and feelings can make it easier to start. Its often hardest at the beginning because when you first start voicing the things you've bottled up ongoing, the intensity will generally be higher than is pleasant for people to be around, and you kinda have to let off enough emotional pressure for a while before the intensity comes down. A therapist could be helpful in doing that without having to unpack the culturally ingrained masculine discomfort with vulnerable or uncomfortable emotions (in some ways, in other ways therapy is harder. But it's private and comes without the normal social expectations of being positive)

Good luck! This is a really hard thing to work through for a lot of men, as a society we really set men up to fail in this way