Taking hydrochloric acid before going to bed can help some who experience nausea during liver flushes, as can a hot water bottle over the liver, or sipping peppermint tea.
Have you done a Colon Cleanse prior to liver flushes, and do you have regular bowel movements daily...at least 1, preferably 2-3)? If the colon is congested with toxic debris, the toxins released during Liver Flushing can be reabsorbed in the bowel and enter your blood, circulating through your body. This can cause fatigue and a general ill-feeling following a liver flush. The epson salts and water clears the recent waste from the colon, but does not get rid of the old, post-putrefactive material. It is important to do a colon and parasite cleanse prior to liver flush.
Also make sure that you are drinking plenty of water. In general, you should consume half your body weight in water daily...and even more when you are doing any cleansing program. Feeling tired is a common sign of dehydration. You may also need to replace eletrolytes that are lost when using the epson salts and water.