When you do an activity day after day you develop what is known as a habit. Habits can be good or bad and smoking is definitely a bad habit. Just like with building habits it takes time to break habits or replace them with a new one. When you quit smoking you will have the urge to smoke at the regular times you normally smoke because of this.
In my opinion, the hardest thing to overcome when quitting smoking is the psychological effects of smoking. To fully understand this you need to look at how you have used smoking over the years to control your mood. Do you smoke when you are angry, trying to calm down? Do you smoke to manage stress and anxiety? What about boredom… The fact is people smoke for so many different reasons and when you combine nicotine addiction, the habit of smoking, and the psychological effects it is very difficult to quit.
By understanding what you are up against you can greatly increase you chances of success. If you feel your area of weakness is nicotine withdrawal then you may consider nicotine replacement therapy such as Nicotine Patches. When breaking the habit of smoking it is better to replace it with a new habit such as exercising or walking when you have the urge to smoke. Dealing with the psychological effects of smoking seem to be what gives people the most trouble, especially stress. You have to remember that millions and millions of people deal with stress each day without smoking and you can too. In fact, you did it before you started to smoke. The key is to find your areas of weakness and plan for them. Use a combination of resources and go into this with both eyes open ready to do battle. Check out the stop smoking help section for additional information on quitting smoking.