Exactly the point, you can't just direct them with words but an action is needed to divert their attentions, if the person is very
close to you, then you must find a good way to divert his attentions,.
Putting him in a place where he can avoid some time playing / gambling and give him some breathing to think the right way, best time to have
some serious conversation and give him some hints that he's already getting engage that much.
A good start to bring him back to reality in life and also to allow him to balance his gambling activities and be reasonable in terms of spending
time and money when playing the game.
usually, instead of playing for fun/entertainment, players take it to the next level and become unreasonably serious about gambling, while i don't really recommend making it as your primary source of income, we cannot deny the fact that there are few people who will do this and a few that changed their lives into something good by playing. sometimes people forget that it was only made for fun and the stress that has been accumulated throughout every game can lead them to something they didn't want to initially such as the things listed by the OP.
i somehow agree with you that one of the best medications for those gamblers is to let them understand that they could no longer regain what they had lost, and if there's a chance they can, it will be all depending on their luck. they should also realize that once they enter the pit they will have a hard time climbing up again, and after telling them that they needed to be slowly separated to that hobby or find another hobby to take up their time slowly just like withdrawal methods for those who are under rehabilitation, but still that depends on the very person if they really wanted to still be able to change their life although things are no longer the same. in the end it is only a matter of how those people can accept the reality they put themselves into.
Those kind of people are called a gambling addict. I've been through there and my life is really messed up back then. Even if you are a gambling addict, treating it as a primary source of income is crazy. A gambler should have at least one source of income to continue the addiction they have. Having none is just like throwing up your life by getting others money just to gamble. A friend or family can help in reducing a gambling activities but it will all depends on the person. As I said I've been there an I received help before from my friends by diverting me but that doesn't stop me until I realized that myself. Don't get me wrong, the support of my friends really helped me realized it that made me change. I guess realizing it by yourself is a new level of matureness that can be earned as an ex-addict.