Half Marathon

I am starting to feel very apprehensive about this race.  I have yet to run more than 8 miles on my own and have a partner that is not 100% sure she is going to run with me.  My goal is simply to finish the race, however, with lack of support around me, I am considering changing to doing the 5K, instead of all 13.1 miles.  Almost feeling like I am sabatoging myself, as I have not been making much of an effort to run farther, however, I am simply not as prepared that I could be.  Trying to be positive but it's getting more and more difficult the closer the race gets.  We'll see...