hmmm looks like many dont know what expectancy is about.
say, in blackjack, if you're NOT counting cards, you've negative expectancy, while the house has positive expectancy.
if you're counting cards, then, you reverse the roles, thus the player reading cards has positive expectancy and the house has negative expectancy.
there's nothing else that can do to turn the odds around for the player than counting cards. obviously, no casino ever allow card counting, therefore, in normal circumstances, you always have negative expectancy in blackjack.
any betting system you use will never revert the negative expectancy, unless you'd be allowed to, for example, increase the bet geometrically every time you lose, until you finally win, but that's not allowed in any casino and even if it would, you'd have to have an infinite bankroll to play.
now, you can play blackjack lots of time without counting cards and still make money. why is that possible, if you have negative expectancy? well, it is because you got lucky.
so, you can make lots of money in a negative expectancy game or in a positive expectancy game. the main difference is while in a negative expectancy you only make money if you get lucky, in a positive expectancy game, you'll make money no matter what, it is a question of playing it enough times until the law of large numbers kicks in.
in trading, the above principles apply like a glove. find yourself a way of counting cards in trading, and you'll be long term winner no matter what happens in short term.