When I first started, I have since then quit, I used them as a stress relief since I couldn't drink at work. I was having a few extremely s***ty days spread out over a couple weeks, so I asked one of my coworkers for a cigarette, then it graduated to just when I was drinking, then it became smoking on my breaks at work. For me at least, I used to equate smoking to work, it didn't help that in the Marine Corps, pretty much the only way you can get a break is to smoke.
As I said before though, I have quit, and I am very happy of that fact. The hard part now is not regressing.
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~=B8's Resident Ninja-Pirate. Please insert liquor, and pour one for Guru Winner, BT=~
http://www.futurama-madhouse.com.ar/fanart/kenneth/bender_auron.jpg