While I agree with the mentioned mistakes that often contribute to trader failures, but I think overconfidence is a big one too that not everyone talks about.  What happens is you have some wins early on and suddenly you think you're the next wolf of wall street.  You throw risk management out the window and go all in on crazy trades and  before you know it the house of cards comes crashing down.

From my own experience, staying humble is so key in this game.  You gotta accept that you'll mess up sometimes.  Trading is a skill that takes years to build. It's a marathon, not a sprint. Anybody who thinks they've mastered it overnight is in for a rude awakening.