Not my weekend

Sitting in somewhere near the top 10 on the first lap, I was feeling pretty good. After a bumpy downhill section which lead to the first water station and some loose granite, my chain falls off the big ring. I get off put it back on loose 10 positions and try to get back into my groove. Then somewhere into the second lap I miss a turn and go back to get on the right course. Not soon after that I get to the same water station and my chain fell off again, this time I go to pedal, but with no chain there to make me go forward I go down pretty hard in the loose granite. Get up put my chain back on, but my rear wheel wouldn't spin... I looked it over quick but I couldn't figure out why. I figured that if I just loosen the rear brake brackets and just ride without a rear brake, but nope that didn't work either (and it probably wasn't a very good idea). So I walked back the the start/finish and handed in my back tag. First DNF of my career, I guess I can't complain since I've had pretty good luck leading up to this. Subaru PRO XCT is next and I will be sure to have everything in line!