Yes, because gambling cannot be used as a stable source of income, management becomes difficult.
Cannot? That tells it's impossible, I beg to disagree with that as I believe it's possible but chance of making ourselves successful is very slim. So let us not use the word cannot or impossible.
Are you being sarcastic here or you actually mean this? PythagoraZ wasn't talking about being successful in gambling but rather, he's talking about making it a stable means of income. Being successful in gambling is of course very possible but you can not definitely make it your stable source of income. The word "stable" means steady and continuous. Your winning in gambling is not always guaranteed no matter how expert you are, this automatically make it impossible for someone to rely on it as their source of income.
Of course, I'm not. Maybe we differ on the definition of stable because what I understand about stability in a gambling perspective is not winning daily or weekly, but at least you'll end up winning in the long run. Just like a casino, they don't win on a daily basis, but they win in the long run. I know it sounds impossible for most of us, but there are people I follow doing sports betting, which they call pros, and they are showing how profitable they are.
Sometimes they will have a losing streak, but since they have a decent bankroll to withstand that kind of situation, they were able to recover until, in the long run, they will still end up profitable. If you live within your means, I think you can survive with your gambling income, considering you are profitable.