Don't do it! I can guarantee when you don't, you'll wake up tomorrow feeling so happy you didn't. No one is making you do this - you chose to do it even though you knew the first few days would be hard. There must have been very good reasons for that even if they don't seem so important now. Get through this and you will get the rewards - a diet that is surely the easiest diet in the world to stick to, and huge fast weight loss.
Just take it as easy as you possibly can till you feel better, and don't worry if you let things slip - you'll have energy in bucketloads soon to catch up xxx