I think it is different for every person Flench.  It is also about motivation, to some degree.  My motivation?  One day I went to buy a carton of cigs, back when they were $25, or so.  I plopped them on the counter and the clerk rings them up,......$50!
I had to look dumbfounded and she explained a new tax went into effect.  I looked down at the carton, slowly pushed it away and never looked back.  The rebel in me would not allow myself to be extorted into paying some sin tax.  Then I discovered I had no side effects at all.  I kept waiting for it.  It never happened.  It pissed me off!
All that wasted money.
Now, there is one thing.  Maybe this is it.  I had smoked myself down to Merit's lightest cig.  The lowest nic and tar one they make (Ultima?).  I was smoking them for a few years.  Maybe that had something to do with it.