Why Is It So Hard to Quit Smoking? Mark Twain said, «Quitting smoking is easy. I’ve done it a thousand times.» Maybe you’ve tried to quit, too. Why is quitting and staying quit hard for so many people? The answer is nicotine. Nicotine Nicotine is a drug found naturally in tobacco. It is highly addictive — as addictive as heroin or cocaine. Over time, a…