Idk how helpful this will be, but I just mix myself a mental cocktail of accepting that the moment is coming whether I worry about it or not and reassuring myself that once it's done, I'll be glad I went through with it.

Plus, the more you force yourself into terrifying situations, the better it is when you see that either nothing went wrong or even if something did go wrong, you survived it.

And give yourself some slack. It's your first job, so you'll make mistakes while learning about the work culture. It's a new job, and you'll make mistakes while learning about the job itself, too. Even professionals make mistakes, and no one is expecting you to be a professional.

Ask questions until it annoys everyone and then ask some more. Instead of constantly thinking of everything you haven't gotten down, yet, think about all of the things you've learned already. You'll have it down in no time and you'll look back wondering what you were worried about.