Annie,
It's all about motivation and will power. Not quitting is the easiest thing to do. Quitting is so hard it seems overwhelming at times. Did you plan your quit day with milestones and reinforcement?
For me, this time, I just picked the next day (which was yesterday). Afterall, why screw around and wait. But each person is different and I've taken classes where you lead up and eventually smoke your last with a high degree of ceremony. Whatever works...good luck.
-determinedtoquit