I recently quit smoking. It has been a month as of yesterday and it hasn't been easy.
I've smoked for about five years and have been trying to quit for just over a year. Couldn't do it. The longest I went before now was four days.
My tactic? Set a goal. It helps tremendously. I decided I needed to save up for a down payment for a mortgage. I couldn't do it because I was smoking a pack a day at $12 a pack. You just need to convince yourself that something else is more important than a cigarette. It's still hard, I still get cravings (although not nearly as intense as the first few days), and I am still quite irritable - especially at work. If you get a craving just think of your goal and how hard your willing to work to get it.
It's possible, you just have to set your mind to it. Cigarettes are as addicting as you make them be.