Actually there's a very nice use of imagery in this piece.

The only suggestions I'd make would be to rewrite the first line of the couplet, and even there, only the first part: I don't think you need to say you are in pain, because the stanza right before it says that quite well.

Instead of "it's he who missed his mark", which is excellent by the way, try "'tis he...".

Again, huzzah!