One thing to think about is 'how do you smoke?' the actual physical process.
My Father In Law was told by a doctor that it was better for him to smoke. He had COPD and was on hospice, living here with us. We thought the DR was crazy to tell a man who was in heart failure and had COPD!!
We figured out why the doctor thought that when Dad was given a nebulizer machine. The deep breathing and the slow breaths seemed to calm him. We didn't forbid him to smoke, but he had to smoke outside because our youngest has asthma. We would wheel him out on the porch, in his wheelchair, and he would turn off his oxygen to have a cig. Later, he would have trouble breathing, and we would hook up the nebulizer, and I could see the same relaxing affect.
The medication that we had to putin there for the breathing treatment would barely be touched before he was relaxed. I know some of it may have been the meds, but I firmly believe that a lot of it was the relax and breath.
I know every person is different, but it's worth a try. I don't mean with a nebulizer, but just make yourself sit and relax, taking the deep slow breaths. I know it seems strange at first, but if you make yourself set a timer, I can't remember how long a breathing treatment took, but anyway, set a timer and make it like taking one of your medications.This is my medication, and I need to go sit in a quiet place (although my place is rarely quiet with 4 youngin's 
), and just rest and breath.