Welcome to the community!
Chantix worked for me, too. Glad it's doing the job for you! EIGHTEEN days is super!!! Congrats!!!
An important thing you can do right now is to educate yourself on what nicotine does to your body and mind. It will help you to understand the fact that you can never, ever have "just one" no matter how long you have been quit. To that end, I highly recommend Allen Carr's “The Easy Way to Stop Smoking.” This easy and entertaining read provided a world of good information about nicotine addiction, most of which I was not aware. I credit it in large part with my success at quitting. You can search for it online or at your local library.
You should also read the posts here and perhaps go to the pages of folks who you think might be helpful. You might visit whyquit.com, quitsmoking.com and livewell.com for the good information contained there. @https://excommunity.becomeanex.org/groups/best-of-ex has lots of blogs written by members of this site with their experiences and guidance. Here is a video to inform you further about nicotine addiction: https://www.youtube.com/watch?v=IpWMgPHn0Lo&feature=youtu.be.
The idea is to change up your routines so the smoking associations are reduced. Drink your coffee with your OTHER hand in a place different from when you smoked. Maybe switch to tea for a bit. If you always had that first smoke with your coffee, try putting your tennies on right out of bed, going for a quick walk, then taking your shower and THEN your coffee! Rearrange the furniture in the areas you used to smoke so the view is different. Buy your gas at a different station. Take a different route to work. Take a quick walk at break time where the smokers AREN'T.
You need to distract yourself through any craves. You can take a bite out of a lemon (yup - rind and all), put your head in the freezer and take a deep breath of cold air, do a few jumping jacks, go for a brisk walk or march in place, play a computer game. Keep a cold bottle of water with you from which to sip. Don't let that smoking thought rattle around in your brain unchallenged. Sometimes you need to quit a minute or an hour at a time. You will need to be disciplined in the early days to distract yourself when a crave hits. Get busy! Here is a link to a list of things to do instead of smoke if you need some fresh ideas:
https://excommunity.becomeanex.org/blogs/Youngatheart.7.4.12-blog/2013/02/25/100-things-to-do-instea...
The conversation in your head in response to the "I want a cigarette" thought needs to be, "Well, since I have decided not to do that anymore, what shall I do instead for the three minutes this crave will last?" Then DO it. You will need to put some effort into this in the early days, but it gets easier and easier to do.
Stay close to us here and ask questions when you have them and for support when you need it. We will be with you every step of the way!
Nancy
