Like many young men I smoked in Vietnam (and the price of a carton of cigarettes was around $1.75 if memory serves). I smoked just about anything with tobacco in it from age 16 to age 24... To this day I can't tell you how I was able to quit cold turkey - but I did at age 24... Best thing I ever did healthwise...
Young men do foolish things (so do old farts - but that's another topic entirely... ).