Boring occupations give addiction a fertile place to start. Back when you could light up almost anywhere, any time, a cigarette provided a welcome sense of progress when things in general might be moving too slowly. Feeding your body and mind an addictive chemical rewards those receptors, creating a sense of accomplishment without needing any real achievement to back it up.
I'd settle for a drink. Something, anything to liven up the tedious wait for quitting time. Hell, give me something illegal, as long as it digs its claws into my brain and lifts me up to a warm, sunny place.
This is the fatal weakness of natural highs. If you get your buzz from exercising and you can't go exercise for a set number of hours, those hours stretch into a bleak desert. I can't submerge into meditation or devote myself to creative projects of my own when I have to remain in the cross hairs for any customer demand between now and our mandated hour of release.
Oh bliss, oh joy. Now someone's bringing in a screaming child. Give him a bottle, dammit. I'm bringing my own, tomorrow.