never touch blackjack where you cant count the cards - you are kidding yourself if you think you can win otherwise
also, 90% may not be far fetched if its 90% non-losing sessions - i have had runs where i did not lose at poker after session was over for like 10 or so days in a row - seems like forever - and depends on what your session includes
but back to blackjack - again dont do it if you do not count cards - bad bad bad