I Accompany Someone for the First Time

So my friend asked me to accompany him for his hymn project in his theory class (which I withdrew from because it was above my experience level and blah blah blah) and I said yes, thinking that it would enable me to get over my fear of performing in front of people and therefore I would gain more experience. 

Ok maybe a valid point but I had less than 12 hours to learn the music I had to play....hymn in CM no biggie, and I learned it in 2 and 1/2 hours of straight practice (I even skipped my oral communication class).

As you can imagine, it comes time to play and I freak out and mess up and now I feel pretty lame and I hope my friend didn't get a bad grade on his project due to my uncalm nerves. In short, I just feel pretty terrible but at least I didn't stop half way through the song?