When we start to feel anxiety or panic, oftentimes our brain is tricking us. It's telling us to get ready for fight-or-flight when there really isn't any danger.
So trick your brain right back. Rather than fight the feeling, wish it on. Sincerely wish it on. Say out loud "ok, you're coming, give me your best shot, I WANT the panic. I'm EXCITED about the panic. This is going to be fun!"
I know, it's counter-intuitive. But anxiety and panic feeds on itself. If you fight it, it gets bigger. So do the opposite. Wish it on!