When you quit smoking, your body goes through several changes (i.e. withdrawal). Everyone is different; some people experience severe withdrawal symptoms and some people experience few if any symptoms. As long as you stay smoke-free, these symptoms will disappear over time.
Withdrawal symptoms may include cough, headache, nausea, gas, constipation or indigestion, fatigue or trouble sleeping, sore throat or gums, dry mouth or runny nose, sad mood, irritability, or trouble concentrating.
You can use nicotine replacement therapy and other quit smoking medications to reduce withdrawal symptoms. It is also important to practice good self-care when you quit smoking. Get plenty of rest, drink water, do things to relax, eat balanced meals, etc.