After reading through this thread I am definitely convinced there is a lot of truth to what cornelius has discovered. What a brilliant discovery it is, too!
I think our "POIS" state is more a reflection of our true selves. It is our underlying state of being, the way we are when you strip away any stress, excess energy, anxiety, etc. So if we are depressed in that state, then we need to just ACCEPT first that that is who we are, and work to improve our lives around that... improve our social life, jobs, diet, exercise, etc. Only when we ACCEPT it, can we finally change it.
I have noticed that my "POIS" was worse a couple of years ago and that was because I had more anxiety and depression and job and social stress than I do today... but my POIS is not completely gone, which means there is more room for improvement. I have to wonder if I will ever completely rid myself of POIS, especially since semen is sort of "life energy" and one would expect to get drained a little bit afterwards as we get older. But I see no reason why I shouldn't have sufficient energy the day after, and that is what I will work towards.