@Robert Gentel,
It's the activities you/we
associate cigarettes with. Those associations become fixed habits:
...Like a cigarette with your morning cup of coffee.
A glass of wine with a cigarette.
A reflex cigarette when one feels anxious or worried.
Smoking as an "aid" to concentration, when you're working on some demanding task.
Then a cigarette to congratulate yourself on a job well done!
The hard thing, when trying to give up, is
de-programming yourself from those associations. Coffee doesn't taste quite the same without a cigarette. That wine you liked so much tastes rather strange now. How do you stop yourself from reaching for a cigarette when working on that demanding task? And how do you celebrate completing it now?
It's difficult.
Successfully quitting might require quite a few changes in how you structure your day, changing your "normal" activities to completely different ones in which there are no entrenched smoking associations.