I've smoked intermittently for years. Whenever I started back, it was triggered by something stressful. I don't know if it is the addiction lurking around even after not smoking once in 5 years. It is extremely calming in those stressful situations.
And as ex smoker, I find it interesting it's not the smoking itself that was 'stress reducing' for me. But those 5 minutes I would make free for myself to do nothing (smoke) and just think.
I once read that smoking is a bit akin to a guided breathing exercise in that way - during those 5 minutes you breathe consciously and in a more controlled manner than usual.
I don’t know if its actually true but it always made sense to me.