I think it would be odd if you didn't feel this way. Up to the morning of my procedure (July 2nd) I doubted my decision, but in the end I'm so happy I choose to go ahead. It is still fresh and I'm still dealing with the immediate after effects but I'm excited now not doubting.
You will have to make the decision that is right for you though. If you feel you can maintain another diet and exercise without the surgery then by all means do it. For me I finally realized I could drop the weight and put it back on 20-30 more times in my life and I wanted it off permanently and felt the sleeve gave the best chance at success.
Others will have better replies and stories but keep talking out you feelings and fears here, with your doctors and loved ones and you'll make the best decision for you!