A couple of things stood out for me with this poem.

Firstly I loved that it was in a letter format. That just caught my attention.

Secondly, I absolutely LOVED that the letter was addressed to your heart. Extremely original!

Thirdly the poem was very dark. I like dark, sad poems that deal with emotion.

"roses of my heart growing strong as the thorns rip me apart "

5/5 from me for just this line alone!! You create an extremely vivid picture with this imagery that it made me have to pause and re-read it again! I honestly think this line itself is enough to base another poem on!!

Finally, the only negative thing which I feel lets your poem down is the punctuation. You need a few more commas and full stops in there because it really distracts the reader. You dont need to take my advice, of course, but I really believe that it would do wonders for your poem!

Nonetheless, a great read!