Even if you are very anxious I think you can search over the internet and determine for yourself that the prep *always* works. In fact, as I posted earlier, it may be a relief for you if you are suffering from constipation. You take clear liquids and the bowel prep prescription(which to me did not taste bad as mentioned by others) and then evacaute yourself multiple times. Use a baby wipe to soothen your anal area since you will be having several bowel movementsFor more comfort - try having the colonoscopy first thing in the morning. I slept at 12, woke up at 6:30, went for colonoscopy at 7:00. The procedure itself was painless. I got sedated and completely relaxed and woke up to find that the procedure was done. No remanants of pain, nothing. I was hungry for the first time in several days since my stomach was cleared.Good luck.