Can someone please help? . – .

One thing: the more you think something bad is going to happen, the more likely it will happen. Trust me. I auditioned for a musical in high school, kept telling myself I wasn't going to make the high note of a song, and ended up messing it up (even though prior, I could do it)--in other words, a positive mindset is good to have. I ended up as the extra--well, one of the many wives of Joseph (lol)--but I wouldn't've messed up if I wasn't thinking I would.
Also, practice in front of peers and family members. That could definitely help!
Oh, and a weird tip that my friend gave me in class--she said her husband has terrible stage-fright, but when he drinks apple juice, it totally changes him and he can actually speak on stage! (I don't know, you can try it haha)
And don't worry!!! You've got this! You'll do fine. If you weren't good at what you do, or didn't have a goal of getting into honor's band, then you wouldn't be doing it. You are totally capable. Believe in yourself! I believe in you :)

The best way to stay calm is to remind yourself that youre not alone in this. Other people trying out are feeling the same things you are! Think of it as not a solo presentation, but just sharing something beautiful that you know. You've worked hard to get where you are and all youre doing is showing someone what you've learned. You are talented and this is your chance to prove it! Again, everyone else is nervous too and most of the time when youre nervous, nobody can even tell.

I've been performing for over 20 years now, and you're always going to have that performance anxiety but the best way to prepare yourself is to expose yourself to other less stressful situations until you learn to work through the nerves. Start by recording yourself, audio, or video (that's even more intimidating), then listen to them. It's also good for the preparation of your piece to hear yourself. Eventually you could ask a friend to listen to you next. Another important tip is to breathe (I don't know what instrument you play), but when I used to get so nervous, I'd hold my breath. Once I practiced finding places to take a breath it helped me stay calm, and also helped me shape my phrases better. There's nothing wrong with you because you get nervous, it's normal and nobody will hold it against you.