Hah I wouldn't worry about it I smoked twice before getting truly high. The first time I got high I was sitting in my friend's car on the way to go get pizza and all of a sudden my legs felt kinda numb and I was like woahhh wtf. Then when I tried to say it outloud I just died of laughter. That was the best pizza I ever had...

But seriously, for the first time (I mean actually getting high) just be in a case with someone who can calm you down if you happen to get paranoid and can just chill.