"There is no skin left untouched.

I am an artist.
This is a masterpiece.
I want to cut more.
It's not that bad. "

This is my favorite part. First you explain how no skin if left untouched, which would assume that you cut in every conceivable place on your battleground. You make sure the reader knows the seriousness of the situation, how far you had taken it, and then you mold it with the next few lines: "I am an artist / This is my masterpiece" Goes to show that to you, this simply isn't slash slash cut cut. To you it means portraying an emotion and feeling in your best piece of art to date. Your masterpiece. This meant a lot to you, as an artist you left no skin unscaved (read: You used every bit of the canvas that you could).

Then lastly, my favorite part when combined with the above, is the realization that the moments over. "I want to cut more / It's not that bad" You had your high. You saw what you did, and the quick crossover from satisfied with your masterpiece to dismayed with the severity of it is intense. Maybe you didn't mean to write this the way I'm taking it, but I love it like this. Before you made the effort to show how badly it was, referring to your arm as a "messy gore" with "no skin visible" - soon the cutter takes over saying it really isn't that bad, let me cut more.

I don't explain things very well, but I wanted to show you that I appreciate that part because to me it's almost the essence of a cutter. Contradiction and irony. Hope you write again next time instead of cutting, we'd all love to read it!

ETA: Welcome to the forums!