Speaking from personal experience, I think I might be highly resistant to getting addicted. I tried cigarettes when I was a kid, then just didn't feel like it any more. Smoked cigars in my early 20s, then just stopped because I wanted to run faster. Used to drink probably a liter of Coke a day plus coffee, then just stopped because I read in a sniper book that caffeine degrades shooting abilities. Haven't had a caffeinated drink in about 2 months. And most recently, I will admit, I would go through a half gallon of vodka a week by myself for emotional reasons. Last time I got drunk was probably 3 weeks ago. I just didn't feel like it any more. I dunno, it's just like substances that I know other people get addicted to, I can try and use, and then just stop when I want with no feelings of needing to go back.
I will say that I've never gone up against super addictive stuff like hard drugs or prescription meds. And with someone like Rush who I imagine has more stress in his life than I can image, I can see an addiction to that stuff being hard to get over. I wish him well with ths marriage. I know he's been losing a lot of weight, IIRC he gave up cigars as well. It wouldn't surprise me to learn that he really is over his addiction to meds. He's been out there in the thick of politics for decades. If anyone deserve a bit of quiet, personal happiness, it's him.