This is why I put forward this advice: before you advise someone to quit gambling as a gambler, you have to hide your gambling activities from them so it doesn't look like you are advising them to do something that you yourself cannot do.
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What other practical methods can we use to help addicted gamblers become better, aside from professional help?
That sounds rather a matter of common sense and not explicitly on something completely associated to gambling, in my opinion. Nobody likes to be advised by someone who does not practice what they preach, that is a no-brainer and when comes to gambling it is rather subjective when we talk of people who are slowly sliding into a step of addiction.
For example, would you believe someone gambling twice a week is in a state of vulnerability and slowly sliding towards addiction or not? You probably think not, but in the eyes of certain religious people gambling that consecutively is a clear sign of addiction in their opinion. Again, it is very subjective.
To me, one of the most important steps to be taken in order to stay away from gambling addiction and even recover from it, would be to find a productive way to keep one's mind busy and away from think about wagering money constantly; I have seen people here in the forum suggesting to turn to video games to replace gambling, but completely turn on video games is not as productive, the ideal solution could be to get a job which is tolerable enough for the addicted person and keeps their mind busy from gambling. Though, the first paydays will be specially challenging to the person as they will be undoubtedly feel tempted to gamble with their paycheck.