Answer:
You use a knife to slice my head and weep beside me when I am dead.
Brown I am and much admired. Many horses have I tried. Tire a horse and worry a man, tell me this riddle if you can. What am I?
I am what no man ever yet did see, which never was, but always is to be. What am I?
My geometry is lost in the night to be found in daylight's break. The rigors of time have torn me to shreds, yet I stand to protect that which lies within. What am I?
You hold my tail while I fish for you. What am I?
Give it food and it will live, give it water and it will die.