Answer:
I drive men mad for love of me. Easily beaten, never free.
Without a bridle, or a saddle, across a thing I ride a-straddle. And those I ride, by help of me, though almost blind, are made to see.
What goes up but never comes down?
I saw a strange creature. Long, hard, and straight, thrusting into a round, dark opening. Preparing to discharge its load of lives. Puffing and squealing noises accompanied it, then a final screech as it slowed and stopped.
My teeth are sharp, my back is straight, to cut things up it is my fate.
I'm the source of all emotion but I'm caged in a white prison.