Started taking my workout seriously, and didn't want to ruin all progress built in rest/recovery by smoking after a workout, and didn't want to smoke before a session to not smell like shit and be out of breath the whole time. Eventually I was up to working out once or twice a day and found i had zero suitable time left for cigarettes, and at that point I barely missed them anyways. I chilled out with my training but didn't pick up smoking again, even on my off days. I just reach for my phone instead.