I've always found it interesting how vastly different our experiences are wrt PIP, sides, results with various compounds, etc.
Some guys can barely have an orgasm on Tren, while myself and others can bust ten in 24 hrs. Some guys can run Sust only cycles with no pain while it cripples myself and others. Of all things ... my first NPP/Test C run two Winters ago left huge knots and crippling pain in my quads. Never heard of NPP doing that to anyone else. Some guys here can run mega doses of Tren while 100mg per week added to Test made me insane. I read a story a couple years back of a guy who ran low dose Deca only for TRT, blasting it once a year, and yet his dick worked fine and his labs were not completely FUBAR. Weird. And very interesting.
My uneducated theory is that our body chemistries are often so radically different from each other that we really don't know what a given compound will do for us, or to us. We have developed general guidelines from years of studies and anecdotal evidence. But for some of us even that gets thrown out the window pretty quickly when our experience doesn't match what we expected. In a sense ... we're all just experimenting.