What worked for me is to take Robin Williams' how-to-quit advice from that cinematic gem, The Fisher King,

"There's only two types of people in the world, those who smoke and those who don't. All you have to do is decide which one of those you are, and be that person"

Paraphrased of course but really it's all about your headspace. Simple and powerful. Ponder it, then go there Monday morning and you've got it beat. Even if you start again, wait a bit and come back to it again when you're thinking straight. Very Buddhist, really.