Hey Ichi,
I used to get the anxiety too. Mostly when I ran out. Sleeping and eating became hard with-out. Not to fear though, getting clean was step one. Now aim to control yourself with it. I find its very easy to want to giggle and be happy all day every day. That will get you no where though. I've modified my habits to suit this pitfal. By staying clean from waking till work is through(5PM for me) then taking a toke or two and eating dinner. One or two more tokes after dinner then just relax. I have party's here and there with more smoking but then take a day or two to stay straight and resume the norm. This also saves lots of money.