Gambing is good if you are able to control it. It becomes bad or wrong when you can't control it like you sold things because the reason is you lose much and because of that little by little your already under control of addiction.
It is, but most of the time control isn't just the factor that could make it wrong. Besides, control is there but only on the first times or in the first few days or weeks, sooner or later if you are learning how to love gambling, you will end up losing it all and most probably just telling everyone that our gambling habit is under control, but it is not.
In my opinion, anything that we do that could affect our lives or the lives of the people around us is wrong.