I have practiced Usui Reiki off and on for 15 years (level II). Honestly, I have only had one time where I felt poorly or 'sick' after a session, and the person I was working on had serious, deep emotional issues. Otherwise, it has always left me feeling energized. As far as energy collection, I personally do Iron Shirt Qigong and microcosmic orbit before hands-on healing, so perhaps this helps as a buffer? Great discussion!