Smokers are actually addicted to the nicotine in their cigarettes.

Most smokers know what smoking could do to their bodies.

Smokers who are trying to quit will benefit from support and encouragement rather than criticism and disapproval.

Two-thirds of smokers wish they had never started smoking and would like to stop.

Some Facts About Stopping Smoking:
When people quit smoking they have to deal with the withdrawal from nicotine, and breaking the habit of 'lighting up'.
They may experience all sorts of different withdrawal symptoms. Not everyone gets withdrawal symptoms, but the most common ones are :-

The craving to smoke.
Irritability/mood swings/feelings of emptiness.
Dizziness/light headiness.
Headaches.
Inability to concentrate.
Sleeplessness.
Tiredness/feeling of exhaustion.
Upset stomach.
Mouth Ulcers.
Sore tongue.
Worsened cough.
Tingling sensations.
Constipation.

Quitters won't experience all of these symptoms, but those they do experience are not imagined, nor are they simply an excuse for smoking again.