If they have that certain control from their emotions then it's really okay for them to gamble as they will not resort to gambling as source of finances but instead a venue that they can find enjoyment, there are people who are engaging to gambling with high aim to win big, thinking that with that mentality they will manage to win and can continue taking money out from the gambling house.
Just like what you said, gambling for fun and not to exceed will keep you away from getting addicted, gambling irresponsibly though will bring you to a big trouble and it will lead you to addiction.
Most gamblers have no control over their emotions and will become increasingly emotional when they experience loss after loss. This will not make them try to stop their gambling activities but make them increasingly try to recover their losses. They will still see gambling as a place to make money, even though that is the wrong idea. If they are willing to learn from the mistakes they have made, they will not want to repeat them and will try to limit their gambling activities.
Getting a big win can happen to you but we don't know when we will get that big win. We should not chase victory because it will not happen easily. We should always be able to limit our gambling activities so that we will experience serious problems that we cannot afford. Playing gambling for fun is enough for us because we only use gambling in our free time and don't make gambling a routine that we always have to do. It will keep us out of trouble and allow us to enjoy gambling as it should be.