This was me my last few years as a smoker. I often tried to cut down on my smoking. I got down to 3 a day a couple of occasions but that didn't last long. I was so on edge and looking forward to my next nicotine fix that I would soon say to hell with it and go back to a pack a day.
Trying to quit by cutting down is torture. You find yourself looking more and more forward to that next cigarette. You are prolonging the time it takes to satisfy the nicotine craving but are doing nothing to get rid of the cravings. Physical cravings for nicotine leave after the first few (usually 3) days that you are nicotine free. Cutting down does not allow you to get to this point.
The best thing to do to get nicotine out of your body ASAP and quitting smoking is how you do that.
* If any newbie is reading this, Allen Carr has a great chapter about this in his book The Easy Way to Quit Smoking. Check it out if you haven't read it.