A series of symptoms such as panic attacks and chest tightness and shortness of breath that occur when you quit smoking are actually due to the withdrawal syndrome that occurs after losing the stimulation of cigarettes that were once very addictive. Because of the long-term dependence on cigarettes and nicotine, including physical dependence and psychological dependence, suddenly stop smoking and no longer exposed to nicotine, the body will be more eager for cigarettes and more eager for nicotine and will produce these symptoms, especially in the first 3 days of quitting. These symptoms include not only the above-mentioned symptoms, but also an increase in appetite and weight, depression, restlessness and even insomnia, anxiety and difficulty concentrating and even mania. As you continue to quit smoking, these symptoms will slowly diminish until they disappear in about 3-4 weeks.