I started smoking at 21.
I was working at a garbage dump, and one day we started getting trucks loaded with cigarettes whose tax stamps had expired. My coworkers and I started loading bins full of them.
I looked at my absurdly large stock of cigarettes, and thought "Hey, why not start smoking? Not like I will be buying cigarettes for a while."
It was nine months before I actually had to buy my first pack of cigarettes. This, even as I went up to about 5 packs a day and developed a habit of handing out an entire pack of cigarettes to people who asked for a cigarette. These people were often awed into silent worship at my magnanimity.
I rapidly cut down to a pack a day, and have maintained that rate since.
A few months after starting, I decided to surprise my mom on a visit to her, by lighting up out of nowhere. Her comment: "You're supposed to start smoking like everyone else: at 12 years old out of peer pressure! Who just decides to start smoking as an adult?!"
I find nicotine does help with stress, while communal smoking is a wonderful way of socializing.
Here is my theory, backed up with science. Caffeine does not actually heighten one's attention and intelligence, so much as shift its peak from where it is relatively useless (around evening), to where it comes much more in handy (one's work hours). In a way, we have a limited daily quota of attention, which a cup of coffee only shifts around to where it is most needed. Similarly, we have a limited quota of patience and even-temper to be distributed through the day. A cigarette can do wonders for distributing one's patience from where it is not very useful (reading a book in the wee morning) to where it can be effective (immediately before or after a stressful activity such as meeting a stranger).
My morning coffee and cigarette are somewhat like tiny, incredibly addictive Doctors able to temporally displace those traits which make one sane, to where they will do the most good. And like little Doctors, the universe itself will end without them.