Has anyone accomplished communicating clearly while in an emotional state, and if so, how?

I saw my T yesterday. She said something and I misinterpreted it (what she said doesn't matter in this situation). Instead of directly addressing it, I accepted my perception as truth and shut down. She did try to get me to talk about it, but I was way too vague and she thought I was upset about something else. I went home crying (I interpreted her words as saying she didn't care about me which logically I know is not true). I cried for 5 1/2 hrs straight and wound up self-injuring. Finally my fiance said I either go to the hospital or I let him call her. He called her, left her a msg, and she called me back right away. She talked to my for over 20mins and we thankfully got everything straightened out.

But if I would have just addressed my perception in therapy, I wouldn't have suffered as much as I did. And right now, I really can't afford to be doing this sort of thing to myself.

I don't know how to communicate when I'm upset. I have never been able to. I hold it in and take it on as my own burden. I need to learn to speak up, but I don't know how. I'm great at talking and writing when in a calm state, but when emotional, I can't seem to utilize any mindfulness or logic