Willpower VS Willingness
Willpower is fighting to stop from doing something you liked (or thought you liked) while still holding it in some esteem
Quitting with willpower is tough because you are still clinging to the thought that somehow smoking is good when you know it isn't. If you hit a big bump in the road you are likely to go back to what you left.
Willingness to quit
Willingness is letting it go, not fighting to let it go, but being willing to not fight to hold onto it so that you may have a new life without the chains of needing nicotine every hour or more.