Take a look at just how your body will respond to you giving up on smoking:

After 1 hour: In as little as 20 minutes after the last cigarette is smoked, the heart rate drops and returns to normal. Blood pressure begins to drop, and circulation may start to improve.

After 12 hours:  Your body cleanses itself of the excess carbon monoxide from the cigarettes. The carbon monoxide level returns to normal, increasing the body's oxygen levels.

After 1 day: The risk of heart attack begins to decrease. Smoking raises the risk of developing heart disease by lowering good cholesterol, which makes heart-healthy exercise harder to do. One day in, your blood pressure begins to drop, decreasing the risk of heart disease from smoking-induced high blood pressure. In this short time, your oxygen levels will have risen, making physical activity and exercise easier to do.

After 2 days: Smoking damages the nerve endings responsible for the senses of smell and taste. Just 2 days after quitting, you will notice a heightened sense of smell and more vivid tastes as these nerves heal.

After 3 days: By day 3 the nicotine levels in your body are depleted. While it’s healthier to have no nicotine in your body, this period can see you experiencing some nicotine withdrawal. Around 3 days after quitting, most people will experience moodiness and irritability, severe headaches and cravings as the body readjusts.  Be sure to be prepared for this as this is where many people stumble and reach for their cigarettes again.

After 1 month: After a month your lung function begins to improve as the lungs heal and lung capacity increases. This means less coughing and shortness of breath. Athletic endurance also increases and you may notice you are better able to take part in cardiovascular activities, such as running and jumping.

After 1-3 months: For the next few months your circulation continues to improve.

After 9 months: Nine months after quitting, the lungs have significantly healed themselves. The delicate, hair-like structures inside the lungs known as cilia have recovered from the toll cigarette smoke took on them. These structures help push mucus out of the lungs and also fight infections.

After 1 year: When you celebrate your anniversary as a non-smoker, also celebrate the fact that your
risk of heart disease has decreased by half and your arteries and blood vessels have begun to widen.

After 5 years: Five years without smoking and your body now has wider arteries and blood vessels, which mean a lower risk of blood clots that may lead to a stroke.  

After 10 years: After 10 years, your chances of developing lung cancer and dying from it are roughly cut in half compared with someone who continues to smoke. The likelihood of developing mouth, throat, or pancreatic cancer is also significantly reduced.

After 15 years: After 15 years of having quit smoking, the likelihood of developing heart disease is the equivalent of a non-smoker. Similarly, the risk of developing pancreatic cancer has reduced to the same level as a non-smoker.

After 20 years: After 20 years, your risk of death from smoking-related causes, including both lung disease and cancer, drops to the level of a person who has never smoked in their life. Your risk of developing pancreatic cancer has also reduced to that of someone who has never smoked.