Any friend that turned into an enemy has been hating since day one. 

If your friend was truly a “good friend” and then for whatever reason turns his back on you, that must tell you something. I’ve personally have seen this type of situation more than I’d like to have. You have to dig deep and really get a good feel who your friends really are. A lot of times there is some type of hidden jealousy or secret dislike and once you become successful, those feelings come out in some of your friends. If this happens, it sucks but at least you know who your “true friend” really was.