I disagree, makoto.
I started smoking (copying parents) at the age of 7 of course I didn't smoke regular or properly then - just the odd stolen ciggie.
By the time I went to high school (11 years) I smoked 10 a day because I chose to and wanted to.
I pretty much gave up for a couple years (5-10) per week.
Then I started again because I wanted to.
At 18 I got my first horse and quit smoking dead because I didn't want the fire risk on the stable yard.
After an incident I started again (again by choice).
Almost 4 years ago I was drinking at alcoholic levels and smoking upto 40 a day because I was choosing too and wanted too.
I quit both on the same day by personal choice, without any assistance.
I was able to do this because I was choosing to do the drinking and smoking therefore I was just as able to choose not to do them.
People on the whole don't care or think "it won't happen to them" or they will quite tomorrow - but tomorrow never comes.
I enjoyed smoking, but I only actually missed it after the evening meal and even that was short lived.