No. You don’t have to start all over. Quitting smoking is a process. Slipping up is common, and nothing to get down about. Most importantly, smoking one cigarette will not undo all the progress you’ve made.
If this happens, take note of what made you waver. Take it as a learning experience. Why did you smoke? Was it after an argument or a disappointment? Were you stressed, driving, on a walk, on a work break, having a drink, drinking your morning coffee, or were you around people who smoke? This knowledge will help you develop ways to avoid the temptation or to deal with it when it occurs.
Whatever it was, make a note and try to make sure it is not repeated. Oh, and don’t make a habit out of slipping up. That’s called smoking.
This information is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment, and should never be relied upon for specific medical advice. If you have any questions or concerns, please talk to your doctor.