Nicotine addiction and quitting smoking:

Nicotine is a powerful drug that affects the brain quickly, and in a "reward" fashion. Nicotine and smoking causes the brain to release an enormous amount of neurotransmitters, or "endorphins". These endorphins mimic the brain's "reward" response to a favorable event. This is the great challenge in treating nicotine and smoking addiction. Smoking or chewing tobacco delivers nicotine effectively and efficiently, and gives one the same positive feeling as any event or activity that is survival based. Warming up after being cold, or eating when one is hungry are examples of this same reward response in the brain.

Our brains are hard-wired to seek out this reward response. Cigarettes or nicotine mimic this response one hundred percent of the time, which is better than most favorable experiences that we have. Nicotine is the most difficult drug to quit for most people, because it creates such an effective illusion to what is perceived as a positive experience. Those of us who don't smoke don't crave it. This is because once the brain is not under control of nicotine, rational thinking takes over and tells you; "it's not worth dying for".

My teacher in addictions likes to say, “If it didn't kill you dead, any reasonable person would smoke cigarettes".