Warrior. This will pass but if you continue to fantasize about that 1 cigarette you are just torturing yourself. That 1 cigarette---it's an illusion. You are craving that feeling it gave you when you were in withdrawal but if you were to smoke that cigarette you would be disappointed because you will not achieve that feeling that you crave. You are not in withdrawal. You are associating the feel good feeling with the cigarette itself and this is the lie.
Good news though. There are other ways to get that feel good feeling. So many more and work better than any nasty puff of a nasty cigarette...and right now you are learning what those other ways are. You never really did because you always turned to the cigarette for comfort.
Feel good moments that mimic the feeling you are craving. (Remember, it's not a craving for a smoke. It's a craving for a feeling. A sensation. Relief of tension or boredom or anxiety)
Cardio exercise. Get your heart pumping. Run walk fast swim bike jog - whatever it takes to get your heart pumping. Endorphins yes. Yes yes.
Orgasms. - I'm not trying to be funny. It's science. Having an orgasm releases a flood of natural chemicals produced by your body including dopamine, oxytocin which is s natural tranquilizer and pain reliever, serotonin - feel good feeling.
Laughing - another activity that releases endorphins.
Meditation/relaxation techniques -. You tube or audio apps. Deep breathing-- focusing on your breath, on the moment. An activity you can take anywhere. Can't always have sex or run but you can always deep breath.
Those are my 4 favorite things. There are so many other healthy feel good "go to's" to discover. Your job now is to figure out which ones suit you.
All that because you quit smoking! You got too much to do. Ain't nobody got time for puffin. Yuck. No going back only forward.
Besides. You are a warrior. And warriors don't smoke.