As the titles says, on my journey I realised one thing - if you do slip up at all i.e. have a drag of a cigarette, or have a whole one... usually as happens when you've had a few drinks - do not instantly think of it as a failure and "oh well I might as well just start again", treat it as a temporary slip up and put it out of your mind and pretend it didn't happen. It doesn't help to start feeling guilty about it.
I had a few of these moments and I can say that with time they happen less and less. After a year I can happily stand around other people who are smoking and I won't be thinking "oh I want a bit of that" - it just doesn't enter my mind now. I think once you get to that stage, you know you have finally cracked it. It took a whole year for me to get to that stage, so stay strong and you will get there also!