My ex's whole family smoked like chimneys, but she had a few bad experiences and essentially went straight-edge outside of the occasional glass of red wine.
Her older brother had serious psychosis issues and was even institutionalized for it briefly. Was on meds, had a few rough years.
Eventually he quit because his then girlfriend got him a job at one of the few remaining Blockbusters and they demanded drug-free, ironically enough. He liked working there, and between him and the girlfriend, quit smoking. Maybe a year later he dropped the schizophrenia meds and started working out. The transformation happened while I was with my ex and it was amazing to see it play out. Like, dude was basically crazy, and in a couple years was managing a video store, had a gf, and got his shit together.
Perfectly normal guy since, at least last I heard.