@lou3 First of all, sending you a big, big hug.
I too was a nervous wreck before my LAR, so I started psychotherapy and meditation. Also Dr. Andrew Weil's 4-7-8 is starting to help me (it takes several weeks of pratice). It is important to share your feelings with your husband and anyone close to you, because then they will understand your behavior and be able to provide better support. I learned it the hard way: trying to protect my parents from being anxious because of my health, I increased my own anxiety ten-fold. Once I told them, I could breathe more freely and focus on being as calm as possible. Writing down what you feel in a diary can also be helpful.
Something else that helped me was to make an appointment with the surgeon and bombard him with about 15 questions related to the surgery, the hospital stay and the early convalescence. Also talking with someone who had gone through the same surgery (mine was a two-stage Turnbull-Cutait pullthrough with coloanal anastomosis, which is a form of TME without a stoma).
Finally, I also took a short trip with my husband to a place I had long wanted to visit, just before the surgery, leaving 2 days for the prep.
Also, preparing things that would occupy me through the hours at the hospital: a book that wouldn't need me to concentrate much, a video game, and crocheting, and a stress relief ball or small stuffed animal.
You might want to take your own wipes to the hospital, without alcohol or fragrance. Pack anything you feel will make you feel good about yourself and relaxed. It might be make-up, your favorite perfume, your favorite hydrating cream or oil for massages, your favorite earings, aroma-therapy difusor, an electric cushion, etc. Preparing your bag with feel good things can help you relax a little.