Should I ask my teaching istant (TA) to reconsider my mark?

I recently wrote an essay and somehow, I only got 68% on it. I thought I would do a lot better. I really want to raise my mark on this essay but I am not sure how to ask my TA. He said it was mainly grammar that interfered with the coherence and the clarity of my arguements. This 68% is really dragging my mark down.