After 72 hours of not smoking, the body will begin to experience a wide range of changes. These changes can be both physical and psychological in nature.
On the physical side, the body begins to heal itself from the damage caused by smoking. After 72 hours, the body begins to clear out the carbon monoxide and nicotine that had been building up in the blood stream from smoking. This process will help improve lung function and breathing. In addition, blood pressure and heart rate will decrease, allowing the heart to work more efficiently.
On the psychological side, cravings for cigarettes will begin to subside. Withdrawal symptoms such as irritability, anxiety, and depression will begin to lessen as well. As nicotine is no longer present in the body, the brain is able to start producing its own natural chemicals in order to regulate mood and energy levels.
Overall, after 72 hours of not smoking, the body begins to heal itself and the mind begins to adjust to life without cigarettes. This process may take time and will vary from person to person, but the benefits of quitting are worth the effort.