I used to want to quit smoking and I'd try and get anxious, panic attacks, trouble concentrating too! I kept trying to quit, would go even a month or two without smoking but, the anxiety and irritability that came from not smoking never wore off nor did it get any easier to stay quit.

What helped? Wellbutrin! I lost the taste for smoking, didn't even crave them. But, the side effects sucked and within the year I started smoking again. After a few months the effects of it sort of wear off I guess and with the crappy side effects like worse sleep issues and lack of appetite, not worth it if I'm smoking!