It’s well known that if you’re playing some betting game many times where the probability of winning each time is less than 0.50 (for example, Craps or Roulette) then no matter what your money management betting strategy is, you’ll lose in the long run. This is one part of what’s called the Gambler’s Ruin.
The standard theoretical attempt is when a player doubles his bet after each loss, the idea being that eventually he’ll win. For example: bet 1 and lose, bet 2 and lose, bet 4 and lose, bet 8 and win (at this point the player is ahead 1) bet 1 . . etc.
The problem with this strategy is that eventually you’ll hit a maximum bet limit set by the House.
Well, that’s all true but money management is still important. When I play Blackjack I count cards (I learned how to do this while in college) so my probability of winning on one hand is extremely close to 0.50. For a betting session, I typically start with 20 units ($100 on a $5 table, $500 on a $25 table and so on). I play until I win 10 units or I lose my 20 units stake or one hour passes (because I’m getting tired and will start to make mistakes).
Using this strategy, I typically leave the table a winner about 60% of the time. (Of course my overall expectation is still negative). There’s a lot of psychology involved too — for example, losing $200 hurts a lot but losing $400 hurts more than twice as much as losing $200.