Nicotine is one of the most addictive substances on Earth. Like caffeine, psilocybin, and THC it is created by it's host plant(tobacco) as an insect and animal repellent. All these chemicals are intended to be unpleasant when they are consumed by predatory insects and animals. They are designed to ensure the survival of the plant that creates them, by creating unpleasant sensations in threatening consumers.
Nicotine has actually insured the survival of the tobacco plant by addicting millions of humans over hundreds of years. It is cultivated and used world wide. As users will explain it provides comfort for anxiety and stimulation for low moods. What users never talk about is the depression that nicotine masks. No matter what people tell themselves about smoking, it's a form of self treatment for depression. Unfortunately, cigarette smoking is probably the most unhealthy activity outside of a potentially terminal drug addiction that can suppress one's breathing. The carcinogens contained in tobacco smoke damage the cardiovascular system, the heart, the brain, the reproductive system, and has been implicated in several types of cancers. There are very few things in life one can do for themselves that impacts their health positively as quitting smoking. It can be a life changing accomplishment that can fan out into many positive transformations.
I have been personally affected by nicotine addiction. At sixteen, I watched my forty five year old father die from lung cancer, that was directly related to his twenty year addiction to nicotine. There are few things that I can do to be of help to other people than to help them stop smoking. I find the process of releasing someone from the release of nicotine addiction profound.