Good luck to the quitters.
I have quit a few times, the first when I was 22 and my dad died of lung cancer. I would say I am 95% non smoker now, although all this chat about smoking really did make me feel like smoking last night! At times of stress it’s an easy fix.
I read somewhere that in 72 hours the physical addiction has passed, after that it is all in your head and I have found that to work for me. Cutting down worked better for me than cold turkey, every day cutting one of the habit fags (the waiting for a bus fag was the hardest) but the big thing was really wanting to, when I got into biking seriously and wanted to race. And making more and more friends who are sporty and despise smoking.
So good luck and stick with it and if you lapse don’t kill yourself over it, get back on the quitting.
P.S and drink loads of water, eat fruit and veg you will find out why soon.