In my opinion we choose our own destiny and what to do in life. If a gambler blames his losses on his genes, most likely he is afraid to admit his mistakes and tries to blame someone else for his mistakes.
I would not say that. In fact everything we do is controlled by the actions of the chemicals in our brain. The illusion of control is completely false and arbitrary. So whenever I hear of addiction, primarily gambling addiction, to stay on topic, I do not believe that the mentioned gambler can control his actions and refrain from negative experiences as much as some people believe that he can.
As I said in a previous post, its all really boiled down to brain chemicals and brain dysfunctions which, if you are unlucky, result in lifetime gambling addictions which do not go away with simple self help or "strict self discipline".
So saying we choose our own destiny is kind of a trap. People who need help get ignored because others perceive it as "their own fault" even though its not really.