win 10 and lose less than 10 is a difficult mission for even the best blackjack player in the world, because the sample size is too small. i believe great blackjack players like great poker players can lose more than ten hands in a row and go on to repeatedly win the toughest tournaments in the world.

perhaps a timed mission win 10 hands in x time (hour) might work? as then you would not need to travel back to the mission giver and wait 10 minutes before restarting the mission.