While nicotine leaves your system within a few days of quitting, the effects of nicotine on your brain are more long lasting than that. Your brain needs time to heal, sometimes up to a few years. During that time, it’s not uncommon to feel a subtle desire to pick up a cigarette. A slip is not a sign of weakness, but rather a sign that your brain hasn’t finished healing yet.   A slip doesn’t mean you are a smoker again. It is simply the time to ask for help and get back to quitting.