True, but you have to account for the chance of ruin. Once you go broke, you have to stop betting. Many traders will continue betting larger and larger amounts of money when they win, but stop betting if they lose big. Making risky bets is quite likely to make you go broke, especially if you scale the size of your bets with the size of your bankroll. The [Kelly Criterion](https://en.wikipedia.org/wiki/Kelly_criterion) is the best way to approach it.