Musician problems

Are there any musicians out there, and how do you deal with BG for a concert??? I just played something really easy so badly because I was 400 and couldn’t focus, I guess. There’s the adrenalin (the fake high), the stress (the real high), the concentration (the low), and the need to not go low on stage…but playing high is a disaster…I just want to be a normal musician and only think about the music.
I’ve got auditions this winter, and concerts all year. Any ideas?
I play classical harp, by the way.

I’m older but noticed your post. I do a lot of community theatre performances, and I struggle with trying to maintain decent BG while being onstage for an hour at a time. The best I’ve figured out is to eat a small, low-carb dinner before, which helps keep my BG stable. Then starting about 30 minutes before showtime, I eat a small snack to bring me up to about 140-150. I also lower my basal rate a little to account for the extra activity. If I get a chance to check mid-show I will. Then as soon as the show’s over I check again and correct as needed. I use a pump, BTW. Hope that helps, and break a leg as they say!