It's an addiction... you have to hit rock bottom.
A casual <insert drug of choice here> user will be less likely to quit than a very heavy user who's been through it and hit rock bottom.
Same logic can be applied to smokers, a heavy 1, 2 or even 3 pack a day smoker is more likely to quit and stick with it once they see the dramatic difference after switching. While a casual smoker won't really be as inclined to quit.
A casual <insert drug of choice here> user will be less likely to quit than a very heavy user who's been through it and hit rock bottom.
Same logic can be applied to smokers, a heavy 1, 2 or even 3 pack a day smoker is more likely to quit and stick with it once they see the dramatic difference after switching. While a casual smoker won't really be as inclined to quit.