Light smoker here, maybe 6 a day...and its just as hard trying to stop from 6 as it is 20.
Smoked for a few years when i was 17, stopped when it started hurting my lungs (i guess my body really doesnt like smoke), stopped for maybe 20 years then on a fateful work trip to S America, some serious technical problems that took a week to solve, thumping headaches trying to work it all out and a 'helpful' colleague who offered a few drags to calm things down a bit...which did seem very theraputic at the time.
3 years later, my lungs hurt in the morning, just like the old days, despite only smoking 6 a day.
I will stop, but its hard when the other half smokes and they're just sitting there...sweetly beckoning me
