Deep breath. It is absolutely nerve-wracking for everyone going into these interviews. I'm almost 30 and have good experiences and scores to highlight, but I'm still nervous about interviews, too. The interviewers know this, and most will try to set you at ease. Imagine that you are both on the same side- you and the interviewer- because you both sincerely want to know if this will be a good fit for you. You're not just selling yourself, although that's part of it. You're also asking them to sell themselves.
They already know they like you, or they wouldn't have invited you. Now take a deep breath, have a calming cup of tea- with some L-theanine powder, if you happen to have it- and the morning of the interview, go for a run or do something else to sweat. It'll boost your confidence and increase blood flow to your brain, allowing you to think more clearly for the interview. Have a list of ten things you want to get across in the interview, in addition to having practiced the questions that are common (out loud, not just in your head). Read over your application and anticipate what they might want to ask about, unless they interview blind.
Now, after you have that list, write out everything in one of those black zippable portfolios, if you have one. They look classy, and you can carry around your notes with you to reference if you need to. I kept all my things in it, and didn't open it or reference it until an appropriate pause. Then, I looked prepared.
Go ahead and pick out your suit and have everything that you're going to bring ready to go. Nothing more stressful than trying to get everything together at the last minute and realizing that your clothes don't look quite like you imagined, so then you're scrambling for something that works.
The calmer you are, the better you'll do. Meditation, certain supplements, and exercise are all very helpful. Beyond that, just know that this isn't life or death, even though it feels like it, and everything will be alright. Good luck!
