Shirty, this isn't a blame game to be countered - she did ... The OP asked for help. He didn't ask for determinations as to whether they should be together or not. That's up to him and her to decide. So is whether he wants to give up smoking for himself or for the sake of his relationship.
Indeed. If you believe you will fail, you will fail. Don't do the "I'll stop when I finished this packet" thing. Or the "I'll stop next Monday" thing. The time is now. " Do, or do not. There is no try" --Yoda The best distraction techniques are the ones that are incompatible with smoking. Go for a walk and leave the cigs at home for instance. Also, don't catastrophise if you have one cigarette. If you don't have another, you're still doing fine.
I put my point across badly because I was on my mobile which is horrible to type on. The crux is that if you change for yourself then all is well, but if you change for someone else then you might be setting yourself up for a fall. Disillusionment and resentment can rear their ugly heads quite quickly in that scenario. I have been there and whilst it might work for some, that level of compromise didn't work for me, no matter how much love was involved.
For me it was like, quick OK I can change that. Then it was something else, then something else, then something else. Within a decade I had changed completely. I dressed differently, spoke differently, listened to different music.... It still didn't work. So now? yeah I've had to change a few things being with my wonderful partner I am with now but mainly single dude habits