The cravings were tough, but for me breaking a promise to Barney would have been much tougher. When I told my mom I had quit, she started to cry. She said she had been praying for years that I would stop and that I didn't need to ever give her another Christmas present. Knowing I had stopped smoking, she said, was the best gift she could ever have hoped for...
So, in my case, I was able to get a LOT of strength from Barney and from knowing how much it meant to Mom. And it's those things that have kept me from ever even thinking about going back ...
That might be the key for someone else who is thinking about quitting. If you can't do it for yourself, do it for your loved ones who will have you around longer if you quit.
EDIT: Contrary to what you see and read, I think quitting smoking has to come from inside. You have to make up your mind once and for all that you are going to quit. Not that you're going to try to quit, but that you are GOING to quit. Take each moment as it comes, and don't be afraid to ask for a little moral support from your family and friends. If you slip, don't worry about it. Just resolve to look ahead and not back... your goal is to quit.
I don't know if it works for everyone, but I like to think that God gave me free will and freedom of choice for a reason. He also gave me strength of purpose. I chose to believe that I could use the very strength he gave me to quit doing something that could very likely end up killing me.
At the end of the day, however, it was the promise to Barney that kept me smoke-free. I don't believe in making promises I don't fully intend to keep. In this case, the only way I couldn't keep it would be if I consciously chose to break it. Talk about using my own stubbornness against me!