Pre-labor anxiety...or excitement?

I had my first official check up with the doc as we count down the days til D-Day.  On Wednesday I was 90% effaced and 1cm dilated.  At first I was absolutely ecstatic.  I mean that just means I'm getting closer to D-Day right?  But then later that night as I was going to bed, it really hit me and I was filled with anxiety.  Can I do this?  Am I strong enough to have a natural birth??  What if I hemorrhage or pass out from the pain?  Am I crazy for even having these thoughts?  Can any of you mothers out there relate with your first delivery??  Or should I be excited?  I know without a shadow of a doubt that my baby Noah is healthy and strong and all will be well with him, I just worry that I won't be strong enough.  Maybe when D-Day actually arrives, all this anxiety will turn into excitement?  Either way, I know I need to get my emotions in check because the only thing worrying does is bring negativity and uncertainty into my life and that always results in me getting sick from a weakened immune system because of all the worrying.  So I am going to do my best to not worry but rather prepare.  My doula and long time childhood friend is so very encouraging and supportive and I know that once the day is here she along with the rest of my support system will give me all the encouragement I will need to have a successful delivery.  I just wish I knew where this doubt came from.  I've been so very, almost eerily, calm this whole pregnancy and have taken pride in my inner strength and desire to have a natural birth, so when this icky doubt crept into my mind, I was shocked that it was so overwhelming.  I guess only time will tell.  

I'll check back in soon...

Liss