It's difficult to control how you do your gambling habit is but I totally agree with you that the only way that you can do it is through discipline, no other way around it however I don't agree on the fact that it's best done when you have got a stable income because I do think that you do not need to suffer from it even when you do have the choice to gamble and not worry about the money, gambling is a pitfall that's difficult to get out of even if you've got the money to survive that pitfall, I'd say that gambling shouldn't be something that's considered an option when you have an excess money.
I agree with your statement and I think you chose the right words to use concerning gambling but I think everything that have a disadvantage also have an advantage as well, i won't advise a poor person to go into gambling or see it as an option to earn a fortune, though some people have been very lucky to make a fortune through it, but it is very rare else the house won't be getting more edge than bettors, I think gambling should be for the wealthy ones who have extra cash to spare for fun and entertainment cause that's the best way to go about it, we all know that there is a lot of risk involved in it and the rate of loses from gamblers in a day should be greater than that of those who win but then no one should be happy losing money that is why it should be meant for rich people who have more than enough with different sources of income, not a poor man trying to survive. Instead of gambling for survival I will rather invest my money in Bitcoin I know they are both risky if done out of ignorance but I could manage the risk that comes with Bitcoin due to it's volatility and i would not up losing everything compared to gambling.