Well, I have seen other people post pretty much the same thing. I believe the general feeling is that if you didn't have any nerves then that would be a bad thing. Being a littler nervous before a flight should make you check everything thoroughly. Maybe if you weren't nervous you might get a bit sloppy in all the checks that need to be done and then that's when you'll come unstuck.
In other words, it's normal (or atleast it is for me although I am currently still training for my PPL)
Regards,
Simon