Rarely do I put poetry into my favorites list, but this one is outstanding. Perhaps in a lot of ways I can connect to it from the view point of guilt and feeling like I did something 'bad' in my past. The story telling and wordplay is also my favorite.

"I did something horrible, and not the
kind of thing where spilling blood
would be atonement. "

This line I want to highlight because in my opinion it is the line that holds the whole poem together. You grabbed my attention because this is where the emotion of guilt starts to unfold and the story starts after.

I am just going to highlight my thoughts in general.

Another thing I love about the poem itself is that it feels like you are writing to/speaking to the person you felt guilty about doing something bad to/with. Almost like you are speaking to their ghost or a memory you are think about.

You are trying to calm anxiety by doing a breathing technique and while it worked a bit, it wasn't enough for this thing you did. That makes the poem more suspenseful and makes the reader feel more sympathetic for the writer. I loved that.

I love the feeling of dread at the end for a couple of reasons. You did not stray from the consistency of emotions throughout and you did not give away what the bad thing was. You did well to leave the reader guessing and this is so well written it works!

I wouldn't change anything personally.