Quitting smoking is not easy, but you can do it. To have the best chance of success in quitting, you need to know what you're up against, what your options are, and where to go for help. 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 is a drug found naturally in tobacco. It is highly addictive -- as addictive as heroin or cocaine. Over time, a person becomes physically and emotionally addicted to (dependent on) nicotine. Studies have shown that smokers must deal with both the physical and psychological (mental) dependence to quit and stay quit. When you inhale smoke, nicotine is carried deep into your lungs. There it is absorbed quickly into the bloodstream and carried throughout your body. Nicotine affects many parts of the body, including your heart and blood vessels, your hormones, your metabolism, and your brain. Nicotine can be found in breast milk and even in mucus from the cervix of a female smoker. During pregnancy, nicotine freely crosses the placenta and has been found in amniotic fluid and the umbilical cord blood of newborn infants. Several different factors can affect how long it takes the body to remove nicotine and its by-products. In most cases, regular smokers will still have nicotine or its by-products, such as cotinine, in their bodies for about 3 to 4 days after stopping.