Quitting smoking is easy. I've done it a million times.If this is true for you then you are one of those people who have a problem with the motivation. It's sometimes hard to stay away from the temptation even after several months. You'll want just another one, just one more to prove you don't need them and all those insane and ridiculous excuses you can come up with. I don't want to sound like a religious fanatic but devil is always awake and waiting for your mistake.
And now you know about it, you're half way to beat it. All you need is to assure you won't fail. How? It all depends on your own personality:
If you are a material type find a trusty friend and give him your monthly salary, or any other amount you would regret not having any more. Tell him he can keep it if you smoke again. He doesn't have to always be near you, there are some blood tests you can buy in the drugstores. They show the concentration of the nicotine in your blood.
If you are a religious type, go to your church and solemnly swear in front of God and all the people present that you won't touch a cigarette ever again in your life.
Now you get the idea. Find something important to you and put it at stake. Risking your health isn't always enough to motivate you. It's too vague and far in the future time. You need something to lose NOW.