Happened to me too. Riding a MUP on my brand-new CAAD-9 (I had just started riding and wasn't comfortable on busy streets yet), when I kid in the other lane crossed the centerline about 10' in front of me. Plowed right into her at 15mph. Knocked her over, I came out of my pedals, went over the handlebars, and landed on the sidewalk. Amazingly she was fine - barely even scratched. I was banged up. The frame on my brand-new CAAD-9 (about 60 miles on it) was bent.

Condidering the circumstances I came out pretty lucky...I had to buy a new frame for the bike but didn't injure anyone or myself. FWIW, the girl's mom (she was maybe 7) was letting her wander unsupervised on the MUP and hadn't bothered explaining to her to look before crossing until after the collision.

I went through the anger/guilt thing for awhile myself, guilt about hitting a child (even if it wasn't my fault), and anger over having to spend $800 fixing a bike I had just saved for months to buy...

Fault is difficult to determine in a case like that. Both parties are at least somewhat at fault. I was going too fast in my collision and the mom of the kid put her (and me) in danger by letting her wander alone without supervision or any kind of rules.

Now I avoid MUP's at all costs and ride on the road 99.99% of the time.