Most people refer to smoking as a habit, and it is, but it's also an addiction. Nicotine excites the nerve routs in your mind, causing cravings when the level is not maintained, which ultimately leads to addiction. Since your nerves have become adjusted to nicotine and "need" it, it can be difficult to disrupt the "need" through the creation of new pathways. A serious quitter needs to be strong willed, but luckily there are ways to help you if you decide on giving up smoking.