Good luck on your upcoming surgery. I would recommend three things to do if you haven't already done them.
1. Take a good before photograph of yourself, so that you have something to compare to after surgery. Many times we are blind to our obesity. We do not see ourselves. Therefore when the weight begins to drop off rather dramatically, we question if this is really happening. Photographs are a good visualization of our success. Many people carry a before and after photo with them, just to remind themselves of their success.
2. Walk 30 minutes each day, every day until surgery (or equivalent exercise). Walking helps the recovery process go smoothly and minimized the pain levels from surgery.
3. Wean yourself from caffeine and carbonated beverages now. After I gave up my 6 diet coke a day habit, I suffered from a week of severe withdrawal syndrome consisting of severe headaches and body aches. I was miserable. You don't want to combine the effects of caffeine withdrawal with the effects of surgery.