For me in my own word, a professional gamblers should have a good making decisions. It's not easy to win in gambling as the outcome of each situation isn't something that a person can accurately predict the results. A professional gambler can find a way to earn money even if it's not direct. A person cannot become a pro if he/she doesn't have self control as it will always result in more losses when you can earn money to recover what you have lose. It is kinda the same in jobs where you put an effort to get promoted. A person that isn't responsible won't become a pro and it can even go self destruction. I am sure you know that soke gamblers ended up stealing.