There are indeed professional gamblers out there, but it takes lots of practice and learning, and it's definitely not something for everyone. You've got to have lots of discipline to make money from gambling, and an ability to adapt to change-
this Reddit thread features a person that is supposedly a professional gambler answering questions about his occupation and other things, and I think this is a relatively interesting read, but it's going to take lots of time to gain the skills to make money from gambling; again, people put thousands of hours into this, and it's definitely not for everyone.
Sometimes, when we talk about professional gamblers, I actually have only seen most people who just managed to get lucky at the end of it all, and in that case, when you have to compare that to a lot of people who were never lucky, you will get more of the latter than the former.
People tend to make the mistake of trying to want to win something big from gambling because they have heard some people winning huge amount of money, but one thing I want to clarify is that, when 1 person is winning, 99 others are really losing badly which is why the chances of winning will always be something difficult to come by.