Most recovered alcoholics and former smokers will never pick up another drink or smoke another cigarette. Not because a single beer or smoke is likely to kill you but because they know how truly hard moderation is. People have far less self control then one may want to believe.
The best way to avoid bad behavior is not through moderation but by making the bad behavior as difficult as possible to engage in. It’s hard to not eat a marshmallow when it’s in front of you but it’s much easier to not eat it if you didn’t buy it in the first place. If you want to do something in moderation then the best way to do it is make it difficult and limit it to exceptional, rarely happened upon circumstances