I have never been a habitual tobacco user. I am a multiple daily user of cannabis.
One summer, I was seeing this girl who I cared for. She smoked cigarettes. It never bothered me because it was HER smoking them. I usually try to avoid contact with second hand smoke because I don't like the scent of it. However, in this case, I was in the state of mind that only a pretty girl can put me in, and even her foul cigarettes had appeal.
I decided to smoke one on the way to Biology lab. Being a cannabis smoker, I smoked it, the entire cigarette, like I would have a joint. This was not a good idea.
I stumbled into lab, feeling quite dizzy and ill. I tried to work, but it was not going to happen. I went outside and tried to vomit, unsucessfully, returned to lab, and fell asleep with my head on the table. I woke, a questionable amount of time later (this was a condensed summer course), and left.
The experience delivered a horrible shock to my system. When I returned home, I slept for five hours.