...Trading is just like any other industry or job or endeavor...only a very select few will truly succeed fruitfully. i agree with rmorse though...that pretty much sums it up: "It requires finding an edge and executing that edge properly. Most traders never find that edge." ...without that, you're just scampering and floating around for dear life...lucky to just break even.
That's because there are no "edges".... other than "front running trades" and "insider info"... both of which are illegal. (Personally, I believe HFT front-runs trades and the revenooers let them get away with it, but that's just my opinion.) However, you can still learn how to put market odds heavily in your favor. Perhaps when I get ready to "hang 'em up", I'll reveal the key to proper TA*.... at least my version of it... there are likely others... Until then, I don't want to deprive aspiring traders of the "ah-Ha" joyful moment of figuring it out for themselves. *Wouldn't it shock you to learn, it will "fit on a Post-It" note?
They say it doesn't work because it doesn't for those who mastered it in 3 days and 2 nights. And, of course, they would never blame themselves.
After running this site for 18 years and talking to countless traders and brokers, both online and in person, and I can honestly say that the reason why the vast majority of traders fail is because they think the key to successful trading is speculating correctly, but in reality the key is actually trade management.
That's the beauty of the markets, vs casinos: in the markets you can Manage your trade. -- in casinos...you're Speculating for an all-or-nothing play.
It's both, actually. IOW.... "WHAT do you speculate upon", and "how do you do so while protecting capital"?
Good question - perhaps the OP or somebody could give us a link to the source of this information. But I suspect 90/10 is just a random number that was pulled out of a hat.
Very simple, between commissions, slippage during market stops, and the bid/ask spread it is a negative sum game; therefore, a solid edge is a pre-requisite to success.