These feelings will pass. It can take up to a week, but usually it passes by the third day. As we cleanse, the stomach shuts down and the real cleaning happens. Toxins are pulled out of our brain, muscles and cells and deposited into our filtering system, the liver, kidney and bowels. The Master Cleanse does this but not as fast as some of the other cleanses, so you are not faced with such a toxin shock at first. Patience on your part will be a reward in the end.
Lean upon Christ for He will give you the strength in your time of need. I have faith that the Lord will see you through this.