I've battled with social anxiety my entire life; for a period of 15 years I was barely functional. I'm still super nervous around groups of people, but I can do most things pretty okay now.

It's absolutely different for everyone, but my social anxiety doesn't apply to video games. In video games, I can separate "me" from "my skill" (character/persona/whatever) and I think it helped me a lot. Especially when voice communications started coming into play for things like endgame raids/trials, and eventually just hanging around chatting.

I did experience tankxiety when I first started XIV, because I didn't really know what I was doing, where I was going, what was expected of me, etc. though. I didn't really want to keep pushing through MSQ dungeons - it was somewhere between self-torture and just being a super draining chore. That mostly passed by the time I reached Brayflox, after knuckling down and spending some time looking at some visual guides for general tank etiquette. I looked up the bosses for each dungeon right before queuing to make mental note of anything that might instantly wipe the group. Every time I did a new dungeon, my anxiety diminished some more. Every time I redid a dungeon, I learned more about it and grew more confident. There was less need to think, because it was nearly always the same, and I could just get into my own little groove and not worry.

At this point I'm every healer's worst nightmare. I push as far as possible in every dungeon my first time in just to see what's what; if we die, well, **** it. It happens. We all learned something. If the other members of the party want to get pissy about it? Okay, that's fine, you guys do you. I'll bail. I can just try again later, and I'll realistically never see any of you again. Even if I do you probably won't remember my name, and I probably won't remember yours. So it's fine.

I use what I know about the game - or other games, or movies, or whatever - to form a basis for entering conversations. It makes it easier to talk to people when you're confident and comfortable with a subject, and it's important to always keep in mind that people aren't supposed to know everything. It's cool to ask questions about things; it makes the conversations more engaging. You don't have to push yourself to always be chatty, or to initiate conversations, and it's fine if you just don't feel up to chatting at any given time. You can just respond with "I'm not feeling very well right now" if people are trying to talk to you, and they'll usually understand.

Take it slow. Breathe. Relax. Take breaks. And don't give up; put in a little work here and there and it'll get easier.