@ally1 - Some once said, "for every setback, there's a bigger comeback". I try to think about that when I'm struggling to get somewhere, do something even understand something.
You'll get there. You've demonstrated you can stick at things with your diabetes, so maybe of you think back to then you can think of some of the coping mechanisms you developed to help you reduce your carbs. Some of those - maybe keeping yourself more occupied, or going for a walk around the block, or whatever, might be helpful when you want a ciggie.
I've never smoked, so never had to give up, so I can't offer you any personal experience.
You'll get there.