Poetry in need of constructive criticism

I'm not a poet; I need to write poems for classes a lot so I'm trying to practice and didn't know where else to post this. Please give me your thoughts on my writing and what I could improve.

A) I feel shame for wallowing in pain

A) The damage is permanent like a stain

B) The harm should be enough reason to stop

B) But I keep letting this happen till I drop

A) I continue doing this in vain

A) I fear my sense of self is going down a drain