its like...

Imagine somebody squeezing your arms tight against your body.  They're doing it from behind, so there's not much you can do about it.  At the same time you have an awesome hangover - your head is too tight, you can't really focus, and it feels like you just want to sleep and get it over with.  But this is early in the day and sleep isn't an option, because you're in work.  You want to concentrate on something... anything, but you can't, because everything is slightly surreal, as if you were stoned.  It all feels a little gritty, like sand in your clothes.  You can't scratch it though, because your arms are pinned.
That's what its like to be on Zyban and give up smoking.  I can't say I'd recommend it, but I haven't smoked in four days.