Same here- its this feeling of hopelessness. When you realise there is nothing you can do or could have done. I have tried my best once i fully realised there was a serious problem, so i initially offered to be there for him and offer an alternative life (which I now know he couldnt really appreciate to begin with). But later on I figured (when nothing changed on his part)- unless I leave and thus not enable him any longer, I am actually helping him with him perpetuating his disease. ANd I wouldnt EVER want that to happen. So the only solution was then to leave. I need to keep on reminding myself that, should we've stayed in a relationship, I would actually be enabling him. And in my eyes, thats NOT love.
Hope that helps a bit... Stay strong Daze