I've never used street heroin but I was a very heavy drinker up until 1.75 years ago. I cut down gradually after having my first child, til the point when I stopped for a year. I had my first drink again in February of 2015 and have had alcohol semi-regularly since then without issue. I discovered that the problem was I drank too fast. I had learned to use alcohol incorrectly, I think if my parents had shown me how to drink when I was 12 - 14 and gradually introduced me to the effects and how different rates of consumption and different forms of alcohol can effect you I would have been better equipped to have a healthy relationship with alcohol. As it was I learned from my friends (the blind leading the blind ... literally). Still, I'm really fucking glad alcohol is legal, because if I was drinking moonshine I would have been in serious trouble and probably wouldn't be alive now.

Can you consume heroin without getting addicted and without necessarily wanting to up your doses?

Yes I was in hospital on diamorphine for 3 weeks (had a little button to deliver it to me). When I left hospital I had oxycontin and endone pain killers, both of which are opiates. I've not used them since.