Hmm. It's hard to give advice without knowing what the issue is, but in the past when I have gotten pissed and needed to talk about it with my partner, I would always start by thinking about what I wanted out of the conversation (I.E. like, do I want an apology, do I want them to do something differently), then I tell my partner explicitly that I need to talk to them about the subject and ask them when would be a good time for them so maybe they don't feel cornered. Maybe if you go into the conversation knowing what you want instead of just venting, you can keep a cooler head and not be afraid to screw anything up! Good luck.
