I found that you have to have a sufficient reason to quit and stay that way.
Just wanting to quit is one thing but having a reason to Stay
Quit is more important.
I quit once and decided that I didn't have enough reason to stay that way so I started again. I was over 2 packs a day within a week in spite of my plans of moderation
When I was sure that my reason was good enough to be permanent I quit and never lit up again. But it took about a year after the Stroke to get to that point
The hardest part for me was the group of physical habits that I had to break. Like when walking thru a door to outside I would have my first puff no later than the third step.
Breaking my hands of reaching for the pack took the most time. A pang of "Need Nicotine NOW" usually comes with that motion.
About 32,000 packs smoked will ingrain things like that