I too vowed to try and lose as much weight as possible in the waiting period before my op but I failed beyond the amount "required" of me as a result of my life long addictiion to sugar and other food in huge quantities. I too found myself stuffing this, that and the other as it would be my "last chance".
However, the day my pre-op diet began, it was quite a different matter as somehow knowing that how much my liver shrank would affect my surgery and possibly future success changed everything in my head (thank goodness something did!!) and I was able to stick rigidly to the rules as I have done post op too this far. I'm delighted with my almost (bar a couple of lb at last weigh in a few days ago) 5st weight loss in 12.5 weeks from start of pre-op til til now. It feels good that I had the courage to finally get proper help, stuck to the rules, walked and walked up until 6 weeks post op and and have now started a proper excersize regime........but I did go a bit mad before my pre op diet........and I don't think doing so means I wasn't ready for surgery to be honest.