one other thing i forgot which works for me is to have some familiar things on hand.

For me it was the skipping part of my warm up. I was really able to relax while skipping, breathe and close my eyes and just think about what i had to do. I'd think about a couple of things because if it got too complex it wouldn't stick but a couple of key things would.

I also had an attachment to my mouthguard. We've been together many years and when I put it in it was like a baby with a pacifier. I just associated some kind of safety and comfort with it.