I was also completely out when I had my colonoscopy. Never felt a thing and when I woke up, I had no after effects. Wasn't even sleepy. Doctor told me I needed to go home and go to bed, but I went about my every day life. Wasn't sleepy. You don't need to worry about the preparation. It definitely works. You'll probably be sick of popsicles and jello, however. I was also terrified but wouldn't hesitate to have it again.