A phrase or advice is usually not well received by those who are only concerned with gambling because the aim is to get big wins.
But they can realize by themselves when they have had the bitter experience of defeat and feel deep sadness for what they have lost.
Once I met a former heavy gambler and he had lost everything precious to him and even his family so he could stop gambling permanently.
It seems that a gambling addict has to experience a bad incident first and then he will regret what he has done was wrong. But it will be too late to regret it because he has lost something or many things that are valuable in his life, for example, his family. And maybe many gambling addicts have lost their families because of gambling. But actually, it was because he couldn't manage his gambling time and lacked self-control when gambling that he forgot to stop and eventually became a gambling addict. We must avoid this because the risk is losing everything precious to us.
We can't control that's the fact! Even how concern you are it always be depends from the person itself if how they will going to control, and same with your statement, they will only reflect things when they already lost a lot, you can continue to remind them about it and not to fail to give them some words of advice to the point that you will spend time with them.
But the last resort to send them away to this situation is for them to accept the help and start changing their own directions and their
perspective about gambling.
I think slowly, that person will realize that someone is always paying attention to him. This form of attention, for example, asks if you have eaten or not, suggests stopping for a while to rest, and so on. Even if they don't care about this kind of attention at first, they will eventually notice it and probably be more open to people by then.
But usually, people don't want to continue paying attention to that person and only for a while. They think that it is pointless to do so until the gambling addict begins to think for himself. Even though that is a form of attention that gambling addicts may not get, who wants attention from those around them.