I can't remember ever hearing anyone talk about post-op anxiety on this level.
I'm going to say what I always say.
First, try meditation. And I don't mean sitting down with your legs crossed saying "om." Meditate by repeating a phrase in your mind over and over and over again. A phrase like, "I am beautiful inside and out," is a great one. Even if you don't believe it, you will believe it if you repeat it enough times because your conscious mind may reject the affirmation, but your unconscious mind is dying for love and acceptance and praise. So that's why affirmations work even if you don't believe in them. All you have to do is repeat, repeat, repeat. Breathing deeply will also help to relax you.
Second, ask for a sedative. There's no reason on Earth why you should have to suffer and your anxiety may affect your recovery. I think it is probably fairly common for people to ask for a mild tranquilizer before and after surgery. You're not asking to be put on tranquilizers for the rest of your life. You just want to have a dozen or so you can take one when things get so bad you can barely stand up. Warm to hot milk can also help act as a sedative, because it activates tryptophan, which is also found in abundance in turkey. The tryptophan converts to serotonin in your brain. Science has lately said this is a myth. Tell that to the folks sitting on your couch practically falling asleep, watching the football game after you eat Thanksgiving dinner.
The great thing about the two-pronged approach is that you can take a mild sedative and then go for a walk, and while you're walking, you can silently repeat your affirmations in your mind. I actually took my affirmations and put them on a cassette tape and played them on my Walkman while I walked. But that was many many years ago, before I even had my surgery.
I still resist affirmations. If you lived a childhood where it was drilled into that you're ugly and fat and not worth anything, it is going to be very hard to stop those negative messages. A lot of people need to see a therapist in order to validate their positive beliefs.
I sometimes have to remind myself that there is a big empty hole inside me that I used to fill with food. Fortunately, that big hole loves to be filled with love.