I think it's like when you plan a big party, or a wedding. You spend a year planning and prepping and getting excited about the big day, and then the big day happens, and the next morning you wake up and say, "now what?" We plan so much for surgery, that once it happens, we don't have anything to fixate on any more. After surgery, you're just waiting... waiting to heal, waiting to feel better, waiting for the number on the scale to go down.
i don't have any advice, but I understand how you're feeling. I've started planning a vacation that we are going to take in a few months, just to give me something else to be thinking about.