If you are not prepared for what you'll experience when you do the Master Cleanse there's a good chance you'll fail. Typically lasting just 10 days, it's easy to see why people just "jump right in" to the Master Cleanse thinking it will be easy. It's not.
Rule number 2 for finishing the Master Cleanse is dealing with aches and soreness. Headaches are one of the most common Master Cleanse side effects, but some people also get body aches.
To reduce aches you should drink a lot of water. It's also good to relax and not push your self too hard when you do the Master Cleanse. Exercising should be kept to light walking and stretching. Your body will be going through a rigorous cleansing process during the Master Cleanse, and won't be able to adequately recover from intense exercise during this time.
Rule number 3 for finishing the Master Cleanse is overcoming irritability. This affects the people around you more then it does yourself, but it's something you need to be aware of before starting the Master Cleanse.
There's more to succeeding at the Master Cleanse then I can cover in this small article. If you are serious about trying the Master Cleanse and want to be one of the people who do make it through the whole 10 days the Master Cleanse Secrets book at MasterCleasesecrets.com is the most complete guide available for helping you get through the Master Cleanse.