There is a discussion on the Trade2Win forum regarding the reason why new traders so often fail. Here is a set of very, very good reasons posted by a member who goes by BSD.
Most newbies fail because they are not in this to make money, they are in this to satisfy a primitive urge to be proven right.
Most newbies fail because they never learn to seperate their ego from their money making needs.
Most newbies fail in this because they never manage to identify what is success relevant; or if they do, they never manage to develop the discipline to actually do it.
Most newbies fail because they never learn to rid themselves of the no-fail identification mark of the eternal net loser: pointless obsession with win rate.
From my experience, these answers to the question cover a very large portion of the new trader population. They reflect the fact that most new traders don’t come into the markets with the right mindset. The ones who eventually succeed correct that. Those that don’t mostly end up quitting out of frustration or blowing themselves up.
BSD also makes a great many other very good comments on the subject. I encourage you to give them a read here.