It is absolutely necessary to have an edge

You can't win without an edge, even with the world's greatest discipline and money management skills. If you could, then it would be possible to win at roulette (over the long run) using perfect discipline and risk control. Of course, that is an impossible task because of the laws of probablity. If you don't have an edge, all that money management and discipline will do for you is to guarantee that you will bleed to death gradually. Incidentally, if you don't know what your edge is, you don't have one. (Jack Schwager)