It wouldn’t be so difficult to quit smoking cigarettes if it werent for the horrible withdrawal symptoms. I personally had a much harder time with the physical addiction than with mental one. Here are some withdrawal symptoms from nicotine.

Depression
Cravings to smoke
Irritable, cranky
Insomnia
Fatigue
Inability to Concentrate
Headache
Cough
Sore throat
Constipation, gas, stomach pain
Dry mouth
Sore tongue and/or gums
Postnasal drip
Tightness in the chest
Cold sweats at night

All of this translates into a very miserable time.  The individual may experience one or more of the above symptoms.  The ones that are very concerning to me are the inability to sleep and the depression.  The others are also very concerning.