I'm growing to like Systemic Exertion Intolerance Disease the more I reflect on it. It was exerting myself which caused me to go from being mildly affected (which I was for the first few years of the illness e.g. full-time education at a high level) to becoming severely ill & chronically affected for the last 20.5 years. Having "Systemic Exertion Intolerance Disease" is a good way to explain this phenomenon it seems to me (I don't think we have a good handle on why this happens i.e. I'm not sure any technical name would necessarily explain it).