If you're getting too paranoid, its probably not a bad idea to take a bit of a break from grass, but if not, here's some things that help me not get unduly sketched while high:
1) Stay in a nice, controlled environment, ideally indoors, with no pressing concerns. Its really important though to smoke only when you are not too worried initially, about obligations, upcoming or current problems, etc, as these can to easily turn into an ineffective, high energy bout with paranoia of all varieties.
2) Don't smoke too much in one setting, if you have any experience at all you should have a rough idea of your "sweet spot" for grass, respective to your tolerance. Or alternately go the oral route, I know that it can often be more intense, but my experiences w/ oral cannabis have been more relaxing, less edgy, and overall more easygoing than when smoked.
3) If you really want some calming aids, try some less risky alternatives before using alprazolam (you don't want to be doing that on a regular basis). For me, some St. Johns Wort (0.9 mg Hypericin) is fantastic for countering bad moods, worry, etc, though you want to try it on its own a few times before mixing with herb. You could also try Kava Kava, California Poppy tea, Valerian, Opium Lettuce, etc, which I have had some, albeit less definitive, success with.
Or alternately, a few leisurely glasses of wine wouldn't be bad either. Kratom also works wonders in medium doses for anxiety (and one of the better cannabis substitutes for unwinding), and synergizes very well with grass, but as always, its nothing you want to be dependent on.