I don't smoke and absolutely hate tobacco smoke, though thanks to my mom and stepdad I was exposed to second-hand smoke for most of my childhood and teenage years. It's part of why I favor public smoking bans; many if not most smokers absolutely do not care if their smoke causes others discomfort or harm. And I don't let anyone smoke in or right next to my house or in my vehicle, and I'll even tell my family members that I'd prefer them to not smoke right before coming over so I don't have to deal with the smell. Oh, and chewing tobacco is an even more disgusting habit, though at least there's no second-hand smoke to deal with. Tobacco is also probably the most pointless drug there is. You don't even get a high off of it. It doesn't actually help you relax (getting your fix with an addictive substance is not "relaxing," it's meeting a physical dependency). Honestly, I wouldn't mind if someone found a way to engineer the extinction of the tobacco plant.
I rarely drink, never got drunk (got a bit tipsy once and only once, and didn't enjoy it), and haven't had a drop of alcohol touch my lips in years; I just really don't care for it. In fact, I've developed an increasing hatred of alcohol because of all the misery and even death I've seen result from it first-hand.
And I've never touched anything illegal. I've never had any desire to. I simply don't understand the appeal of getting high, and risking jail time to get high. I never went through that "rebellious adolescent" phase as a kid, so I never did things just because "Society/teachers/parents/church says it's bad, so it must be awesome and will make me cool because I can stick it to the man!" Even if pot was legal where I live, I still wouldn't touch the stuff, because it stinks, it's not good for you in and of itself, and I have no desire to get high. And harder stuff... well, you have to be an idiot to try in the first place.
I've only ever taken OTC medicine as needed and as directed. I've never taken prescription medicine that wasn't mine, and whatever I was prescribed I did so exactly as directed.
I suppose caffeine counts because I drink soda & sweet tea and I enjoy chocolate. But I don't consume those things because they have caffeine in them. It just happens to be an ingredient. And I've never tried pep pills or energy drinks.
TL;DR, I take substance use and abuse very, very seriously.