Well if so far you have gotten anxious every time you've smoked then it's in your mind that the next time the same thing is gonna happen, so it will...

Find a nice calm private spot, find a nice wooded area where no1 goes and drive your car back there, have some friends around you, and light up, another important thing is clear your schedule so there is no pressure to act sober right away, just relax, put on some good music and breathe. Don't drink when you smoke because booze is a depressant, it shuts off controll centers in your brain so it becomes hard to remove negitive thoughts once they take hold...

happy tokin!!!