You don't even need to consider the other gamblers. If you only consider a single gambler in his or her entire life, you'll see that the amount they bet is more than the amount they won. Pretty much in every single case.
There are a few outliers though, but extremely rare, and more common in the past when the odds where not as bad for the gambler as they are today.
Yes, you are right. We need to pay attention to ourselves because we have to prevent ourselves from experiencing many defeats. And let it be if there are still people trying to make money from gambling because maybe they think they can still get it even if they have to lose a lot of money. But it wouldn't be worth it because it would be like spending money on gambling without having any plan. We really have to avoid this so we can still enjoy gambling properly. Making money from gambling is not as easy as if we work because if we work, we can earn money.
It takes a lot of money required to establish a casino, so when we win, they already know that they are capable of offering to us the said amount they gave as for winning, but they also know that not everyone will make it to winning because there will be varieties of attempts on gambling from different gamblers using different approach which they were also aware of that not all will eventually work out as planned because of the winning chances being too low compared to loosing, but occasionally some gambler hit a big run by winning heavy amount.
And that's why the casinos will get the money more often than the gamblers. Casinos can find that if they run lots of great promotions, they can bring in more gamblers for those promotions. And that's what many casinos have done, especially trusted casinos because being trusted can get more profits. And meanwhile, if gamblers had never realized it, their losses would have been much greater.
@Fredomago has said it all, you do not get to make money all the time, the house will always be sustaining its activities from our losses and it will take a clever gambler to be making money, yet not all the time. For this, consistent winning will never be possible, if this is possible, the house will go bankrupt and it doesn't make sense.
And the advice you gave on taking it slow is not a bad one, when the money is divided for more gambling is better than losing it at once.
Only lucky gamblers can make money from gambling, while unlucky gamblers will only have more to lose. This is where we have to be wise in betting and see what percentage of wins we can get. If we don't know the winning percentage, it's better if we don't try to chase it because it's in vain. We just need to enjoy the moment of gambling and don't use money that we can't afford so we can save the money for the next day.