Wow, talking to a few people about this lately and i've been hearing the same thing again and again in regards to paranoia. Smoke pot too often, especially on your own, and you begin to succumb to the introspective nature of the drug. After a while you'll start getting a little too aware of yourself when you really shouldn't be worrying.
I don't know how often you smoke, or when, but can i suggest you stop smoking for a while, and when you feel positive about your mindset again, just limit yourself to smoking socially with your peeps.
I think the method of smoking plays a part too. A joint is nice and casual, cool. But a buckie is like a punch in the face, too intense. Not cool. When i was dealing with my own smoking paranoia a while ago i found the gradual, progressive way i got stoned from a joint was a lot easier on the mindset than a rogue lungful from a buckie or the stovetop.
Nowadays i only smoke with friends on social occasions.
Paranoia sucks, but you can't just "smoke it off". I don't think it's something you can get better at avoiding. Best thing is to take a break, and change the way you do things.