With the pre-op, most people seem to find the first couple of days the hardest. I can only speak for myself, I found I had niggly headaches and felt quite tired for the first few days. If you've ever done anything like cambridge or lighterlife you'll know what it's like!
Personally, I found that after day 3 I was fine with it, and as it got closer and closer I found I calmed down and started looking forward to it.