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So I don't really think that gambling every day is almost similar to pro-gambling because it's still at a different level and casual gambling CAN'T be considered a real job.
Basically, the more often people bet, the greater the chance of winning and also the increase in the number of losse. Someone who would be said to be a professional gambler is someone who relies heavily on his skill and expertise in gambling, has a mental and style. But all of that will still depend on luck. I just assume that all gambler who are able to control their emotion and manage their finance in gambling will be called professional gambler.
The more they bet the more they make money, they would not be professional in their field of venture if they don't trust their skills and have proven that they are really good at gambling.
Professional gamblers does not gamble for money, they consider that they are doing as their job, unlike majority of the gamblers where they just gamble and have fun, so they likely lose money. Professional gambler choose their game and they know the games that they have an edge and they focus on it.