I can only speak as a former smoker, and I have to imagine that your addiction may be a bit more difficult to overcome. But here's my advice anyway ...
own up to the reality that you have an addiction,
Commit yourself to belief that the most important thing that you have to do from this minute on is to not indulge. Nothing else is more important.
Talk to yourself. Explain how "just one more" can never be just one more, it will always lead to another and make it harder to start over. The need is a trick by a habit that's trying to kill you.
Read success stories of those who successfully kicked the habits.
Find a doc that will prescribe anti-compulsive behavior medicines. They aren't addictive, and they may take some of the edge off.
Don't be tricked by the idea that with just one I can get on with my life. You won't. The only way to get on with your life is to overcome the addiction.
God bless you. And know that people that you don't even know are cheering for you and praying for you to succeed.
