Haha, well maybe thye cigarette thing is a blessing in disguise! *cue anti-smoking commercial here*

. Its very common for anxiety to just hit out of the blue like that and for the person to become fixated on the symptoms they felt at the time. For you, you think about your breathing etc because that is what stands out most for you. My sudden on-set of bad anxiety happened while I had the stomach flu, so I tend to focus on my stomach and nausea etc.
To help you out, you might want to try some relaxtion techniques, especially some that focus on breathing. Maybe try some yoga or meditation to try and shift your mind away from the worry.