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If someone has already accepted their gambling addiction and managed to stop gambling, it is synonymous with willpower.
But the paradox is that if you have the strength and conviction to stop gambling, anyone could come to the conclusion: "Why not just control it and that's it, without needing to quit gambling completely?".
Which brings us to this questions:
Is it harder to control gambling or limit it without falling into excess than to stop gambling forever?
Why is the effective strategy not moderation but absolute abstinence?
It's a matter of choice, people make decisions when it comes to gambling based on their experience. There are people that decided to control it and gamble occasionally and people that also decided to stop totally, both categories of gamblers might have different reasons as to why they are taking that step. It's harder to stop gambling than controlling it, but both requires a lot of discipline and will power