Literally every step of the way he could have done something. This is an unusually clear cut case of someone's actions leading to the outcome that they experienced.

There are attitudes that a community can express which will help or hinder, but there is no escaping that in this specific situation, to get a different outcome Jack had to make different choices.

I'm relatively neutral on drug addictions as a character flaw, it is very easy for me to believe there are people out there who would be making a logical choice to turn to a few moments of reliable pleasure in an otherwise miserable existence. I wouldn't touch hard drugs myself for fear that I would enjoy them. But, nevertheless, the only person who was in control of the outcomes here is Jack.