Don’t plan to stop smoking tomorrow or at some other time. If you say this is the last cigarette, the one after it will also be the last one, and another one and another one. It will never be the last one. You have to make the decision now.
You can stop smoking right now; it is only your willpower, only your wish and only your decision. Promise yourself not to touch any cigarette in your life anymore even if you die because of it. I can guarantee that you will not die without smoking.