Commitment is 90% of the trick. Make sure you've got shorts that will go the distance (I'd highly recommend a chamois cream, like Assos, or Butt Buttr (or whatever it is called) or something), but you ARE a real rider, just to even consider it. Stay hydrated, and stay cool (dump water on your head on a regular basis if you feel yourself getting hot), and keep fueled. You'll be fine. More than fine, in fact. You will be a Cycling Goddess!!!!