In my opinion, it depends on the individual. When people are playing, they need to monitor how quickly their bankroll is depleting and, based on that, devise some way to reduce the rate at which it depletes. This also depends on how people play; they need to decide when is the right time to increase their bet.

They can't act on emotion. For example, they placed $2 on a multi-bet and won $20. Then, on the next bet, instead of continuing to place $2, they decide to increase to $6 on each bet, resulting in a losing streak and losing their entire bankroll. This type of mistake is very common, as I've seen.