So far, I have not seen anyone made a successful career in gambling although I don't so much know what you mean by a successful career. Gambling is a game of luck and sometimes we might not have the time to or focus to be making profits like the way we use to since nothing is constant.
It is very important for us to learn new things so that when the old things or pattern we are doing or using becomes fade out, we can always look for new ways to make money. Since there is no guarantee that we are going to be making consistent profits for as long as we bet, it is very important for us to make sure that we don't see gambling as a major source of income or only source when we don't have something doing.
We know there are a few professional gamblers out there as their careers are legendary, but at the same time the number of professional gamblers is very low compared to the huge number of people that likes to gamble all around the world, so it is not strange that most of us has never met a professional gamblers in our lives, however it is also possible we did and we are simply not aware of it, as professional gamblers prefer to keep their success a secret, otherwise they will be asked over and over again to reveal their secrets.