For me it was mental. A cigarette with coffee was a natural event and I couldn't imagine not having a cigarette after a meal. I hung on to those few for two years after
vaping took away the rest. Going from 2 PAD down to about 6 or 8 a day the first week I vaped was a miracle in my case. I continued on for a long time as a vaper and a half pack or less smoker.
What changed my thinking was when I started
vaping concurrently with my after dinner cigarette. I'd take a puff and then take a vape, back and forth just to compare. I began to notice that the vape tasted good and the cigarette tasted nasty. Mentally, I began to decide that vaping was better for me and tasted better. I didn't need the cigarettes I thought I needed. One day, I stopped smoking and started vaping with morning coffee and after meals. It was easy and not one withdrawal pang hit me once I quit those last few and continued to vape.
It was a mental thing for me. I just thought I needed something more than vaping.