My biggest pet peeve is when an action/adventure type anime takes forever to get to what they set out to do with just talk no actual action.
Like One Piece's Alabasta Arc was a perfect example of it. I left the series for a solid like 6 months before going back to it because that arc was so tedious to watch. Tons of episodes of what is going to happen, and what needs to happen, but no episodes of actually doing what needs to happen.
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.