Gambling are forbidden by Muslims and they think it is sinful. But I saw one Muslim(
https://bitcointalk.org/index.php?topic=1571457.0) is also a high roller who bet 1000 ETH per bet, maybe he is happy about the profit, but I think his Allah is angry. LOL.
No matter what religion do you belong its normal for us to commit mistakes because we are just humans by the way but its up on their decision if they obey your commit such mistake. For me its not a sin if you treat it as an entertainment but if you already risking all your money and it compromises your life and your family then it would be a very big mistake.