I used to smoke off and on for well over a decade. I was well aware of the negative effects it caused on health, finances and hygiene. It also tends to create a predictable routine which could be easily exploited by an enemy. But none of that was the reason I quit.
My reasons were simple and selfish. I found myself unable to breath as deeply or for as long as i should have been able to, while doing my Qi gong. In many movements my breath would burn out at the 50% point. This affected my Qi cultivation, which in turn affected my power, both magical and martial. A few days later I received my first attunement into a system of energy work. Out of habit, I actually lit up a smoke within a couple hours of the ceremony and flavor and texture of the smoke gagged me…big time. Over the next few weeks as my body began healing and purging energetic blocks, I really began to experience the change in performance. Make no mistake, power and control are directly proportional to your ability to breath properly.
On a side note, entertain doing some research on Wim Hof… He is in a league of his own as far as meditative self regulation goes. The ability to breath deeply, and of course properly, is the an absolute non-negotiable component of the Wim Hof Method.