In this scheme you increase your wager by one unit after every loss and decrease it by one unit after every win. For example, with $5 units, you bump up your bet to $10 if you lose the first bet, then drop back down to $5 if you win the second hand. However, you never go below your starting unit, no matter how many hands you win in a row.
The D’Alembert may be a good way to keep your mind occupied, but computer simulations consistently show that no progressive system improves your overall results. Again, you encounter a lot of small wins punctuated by big losses.
Another myth is that knowing when to quit saves you money. But quitting just postpones the inevitable results until your next trip. For example, you get off to a great start during a three-day jaunt to Tahoe and find yourself up $200 the first hour. Quitting early may have some positive psychological and emotional benefits, but it doesn’t make any difference in the long run. Your gambling bankroll continues on the next trip, because your money, the dice, and the cards have no memory of what previously happened. Playing less time overall in a negative expectation game can save you money, so in that sense, quitting has value. But if you plan to play 20 hours of roulette over the next year, it really doesn’t matter how you split the time up per trip.