I've done the Master-Cleanse diet and felt great. I hate the salt flush and instead I used Colosan (oxygen based colon cleanser). It has the same effect as salt flush minus the nasty salty taste. If you only eliminated once during the 8 days, you'd definitely get sick because the toxin is recirculating in your body.
So next time give Colosan a try. There is another brand Oxypowder that people prefer because of the convienience but it doesn't seem to work for me.