The discussion about mental and physical pain brings us right back around to ataraxia and aponia all over again.
As time has gone on, I have come to a (semi-firm) belief that ataraxia is not about rooting out every single disturbing fear and anxiety of every variety. To me, ataraxia is about rooting out the existential dread of fear of the gods, of death, of post-death punishment, and similar unfounded fears and anxieties. Ripping out these fears and anxieties leaves behind a rock solid foundation of calm tranquility when it comes to the big questions of life, and once that foundation is laid, it is permanent -- IF you've truly internalized it! If it's merely an intellectual acknowledgement like "yeah yeah no need to fear gods. Death is nothing. We all get that. Okay, got it" it could come back in times of stress and hardship. You have to KNOW IT, in your bones, when waking and sleeping.
It's a similar case for aponia, but I'm still working out the details of that. I don't think it means what we usually think it means. But I'll get back to you on the specifics.