I am physically fit, enjoy academic pursuits, and spending time socializing with people. I have noticed some circumstances where I feel great one moment and instantly drained the next. For example; I take anatomy and physiology at a university, feel great for the lecture, but after I work on the cadavers in lab I feel like I can barely drive home. I have had similar experiences when talking in front of large groups of people, after confrontations, at the mall, and in bookstores. Is this normal? My wife is asian and mentioned having some sort of talisman made to protect me. Are there exercises or something that I can do that will help to bring up my endurance?