Hey There Dizz,
After many radiation treatments my sinuses were getting clogged and the nasal spray helped open them up so I could breath easier with that mask on. Not being able to breath is bad enough, but add the mask and, for me anyway, it was a recipe for a full blown panic attack. Another thing that helped, which is probably done for all patients, but they gave me a foam ring to hang onto with both hands over my stomach during treatment. It made laying on that steel slab much more comfortable along with a warm hospital blanket. Every little thing helps. I hope they'll let you bring in your own music. Most treatments last about 3 to 4 songs, depending on which ones I listened to. Lynyrd Skynyrd has some good long ones. Oh, and one of my favorite artists is Diana Krall. I've never really been in to Jazz, but her music is fantastic. She has a song called "Peel me a grape" that lasts almost the whole treatment. Believe it or not, I found myself wishing the treatment wasn't over a couple of times just so I could finish listening to the song that was playing. LOL!!! That was when I knew I had accepted the reality of this, in my mind, barbaric treatment.

As I said earlier, one thing that truly helped me besides the music was just believing every time they locked the mask down that it was a good thing and any cancer that may've been left after surgery was being zapped away forever.
I had two rounds of chemo. Fortunately the anti nausea meds really worked. Besides lethargy, I hardly had any side effects.
Oh yeah, one more thing. When they fitted me for my mask, they also fitted me for a mouth guard, but they did not do a very good job of molding the guard to my teeth. Be sure the guard is as comfortable as possible for your bite.
You'll do great! It awesome that you'll have two things to celebrate when this is over.
Take Care ~ Thankful Girl