Don't worry about it. I hope I didn't force you to submit your translation.
I'll read it, and see if I have any suggestions.

I think you did a great job at translating this :D Well done! Especially for your first translantion. I am a naive Spanish speaker and believe you caught the essence of the song well.

I agree with cat: I think you did a good job. I,personally, don't work with poems; I think they loose in translation, and I don't see why you shouldn't be literal, particularly in a case like this where the poet expresses things his own way, not necessarily interpretative, or grammatically correct.

I don't give you suggestions for corrections, although I would say certain things in a different way, just as a matter of style. In any case, my language is Spanish, you are the English one.

Thank you for your work. Keep it up!

I didn't make any comments before but, now that you ask, I will:
1. I don't quite get the intention of the title. To me, a 'coraza' is something strong and protective, and the song says she is "small and sweet', still, if she 'hides her feelings in pride' maybe that's the purpose of the 'coraza', to protect her heart. The name is also applyed to men, in the medieval ages, that fought without lances. At any rate, since the author uses two substantives, I would do the same, and say, "Armour Heart".
2. I would make the two first verses a little more poetic (?) by saying, "Because I have you and I have you not", and finish the poem the same way.
3. The verse "because you are beautiful from your foot to your soul (your being)", i think it would be better "because you are beautiful from foot to soul", and I never use parenthesis in the lyrics, let the readers interpret it; you can always write foot notes.
4. "if I do not see you", the original says, "if I do not look at you".
5. "but you are better where I love you" could it be "but you are better where I want you"?
6. "and you are cold" = "and it is cold".

As I told you before, my suggestions are a matter of style; you are the author.