I don't talk a lot about tournaments. So here goes.
Enjoy yourself. That's always the most important part. I enjoy Regionals because they give me an opportunity to see people who don't live close to me, I enjoy the experience of travelling to new places and the opportunity for photos of places and people, and I enjoy the experience of playing a game I love. Find those things that you really appreciate about the experience, and when you're talking with someone about a close game you just played or talking with friends about whatever you want, just stop and realize "I'm having a good time, I'm enjoying myself and doing something fun with people I enjoy being with.", that's the biggest part of any Regionals for me.
It's important to understand that you shouldn't have to do well at a tournament to enjoy it. If you feel pressured and you're thinking "I’ll be a nervous wreck and just not enjoy the experience overall.", I won't lie, that's hurt me in the past over losing games that really shouldn't have affected me that negatively. Having results is really nice for whatever tournaments you go to, but even as an incredibly competitive player you have to realize you're not going to do well and every event, you're going to do terrible at some and that's okay. If you crash and burn with a 0-X record, play a terrible deck, and make a lot of misplays, even at the end you'll have a story to tell about "That Regionals you did
so bad at" that you're comparing with other Regionals. When you win a Regionals, you'll look back at that kind of tournament and think "I started there, but I've ended up here. I'm a better player now."
I think it's also very important to have the mindset of just going in to play the game you enjoy, just as if you were going into a local league to play at a small tournament, only just devoting the whole day to it rather than a Saturday afternoon, for example. You'll walk into the venue and see hundreds of people, but you'll only be playing 1 person for each round you play. If it helps, you don't even really have to think about them.
Make your Regionals an experience you won't forget. Especially your first. You wouldn't be going if you didn't want to, nervous or not. Have fun, play a deck you enjoy, and take the best you can out of it.
Good luck!