I agree with what everyone has already said about doing the best you can do, not over-analyzing, and trusting the system. Trusting the system includes something WCsweet<3 mentioned--the fact that actives may expect you to be a little nervous...and that's okay! If you need an analogy for reassurance, it's similar to a job interviewer who knows that the candidate might be a bit nervous during the interviews.
The other thing might make you feel better is that you and the other PNMs might not be the only ones who are a bit nervous. Some of the sisters who are talking to you might be a bit nervous too! I know this can be the case for some sisters, especially ones for whom it is their first recruitment "on the other side" or ones who might be more shy/introverted.
As far as calming nerves when not at recruitment events, I think you just need to accept that you're doing the best you can and keep it out of your mind! I am the queen of over-analyzing things, so I know first-hand how hard it can be to keep things simple, but really just try your best not to over-analyze recruitment-related events. Study, watch TV, exercise, meditate, have a laugh with your friends, etc.
The most practical suggestion I can make is the following: if you do have time that you can spend over-analyzing recruitment-related things, use that time to keep up with and even get a little ahead in your studies if possible. That way, after you've hopefully accepted your bid, you'll have a little more leeway/extra time to hang out with your new sisters.
