Jim’s (Mark Wahlberg) entire purpose throughout The Gambler (2014) is self destruction. He’s not an addict. He’s not out of control. He makes every poor, deprecating decision throughout the film on purpose to the point where his incorrigible nature becomes hilarious. When his millionaire mother (Jessica Lange) takes over a quarter million dollars out of the bank so Jim can pay his debts, an act that destroys her inside and ruins their relationship, Jim immediately goes and blows the whole sum. He’s just that kind of guy. He’s desperately fighting mediocrity by searching for rock bottom, and nothing sends you quicker down the spiral of desperation than ostracizing your own mother for a few minutes in an underground casino.
It’s never really that obvious (or understandable) why Jim is so hell-bent on destroying himself and losing all his money, but it’s an obvious character move for a guy with those tendencies.