I dont think its endorphins either although it does feels like a "high" in contrast to the lows caused eating crap for years and years. Its like a fresh and weighless feeling, all the cares of the world feel totally gone. Yes I wish these experiences lasted longer. I think either they are glimses of how we could feel when we get all the toxins/stored trash out or they are memories that were stored in the liver or cells that get released during cleansing.