You went too fast for a hundred, Most 100's are not done at that pace
until the horse is a seasoned competitor. The horse just wore out. Now
this is just in my opinion! Try pacing yourself slower and I believe you
will have plenty of horse left next time. I would go back to 50's for
awhile then work up to 60's then try 100 again.
Chief Black Arrow -retired Appy
Moonhill Dandi -current mount- 7/8 Arab