I was a smoker for ten years, and I quit smoking some seven months ago. Much like you, I couldn't wait to finish my meal and have a smoke - and I never knew why this was so... In my opinion, it is all in our minds, and I can say this because I stopped smoking by deciding to do it, and never smoked another cigarette again. Therefore, try to understand that you do not have to light a cigarette as soon as you eat, and you will probably manage to avoid this habit. Try waiting for some time to pass by before you reach for the cigarette after eating, and you'll see that it actually can be done.