This is a very interesting one. Those who use willpower to give up smoking, and who make quitting a personal battle, tend to report lots of withdrawal symptoms. These are often quite vague, but common ones include irritability, tension and insomnia. This isn't surprising - you're obviously going to be tense, irritable and have trouble sleeping if you are being denied something you really want.
With this product, you don't stop smoking until you feel ready, thereby minimizing withdrawal symptoms: Hypnosis for quitting smoking
The fact is that if you can get yourself to the place where what you desperately want are such things as happiness, health, personal success, fitness, more money etc, the feeling of being deprived goes away. In fact, you are filled with a feeling of success and achievement. There is nothing to withdraw from. This explains why people stopping smoking the natural way report that they find it surprisingly easy.
For further ideas and advice and ways to stop smoking, visit the substantial resources section of this site - Stop Smoking Resources