Hey! That was really good, especially inthe sense that it explained feelings and a heart, and how a heart is fragile... The only tip I can't give you is in this first paragraph (please dont take it's personally, I really really like it, but I thought I'd share my opinion with you)
It's not entirely made of you
Yet I sit here writing this poem
Crying over you
Here, i noticed that you arent rhyming as much as saying 'you' twice... and also,this one is very much my own opinion and really not important at all, but I always find it nicer when you don't remind the reader that you wrote a poem. When someone reads your work, of course they're going to notice its rhythmic quality and know that you did write a poem, but youshould get across your feelings and not what you're doing at the time. It distracts from it the tiniest bit... If you don't agree, feel free to ignore these ramblings hehe, but I thought i'd give it a try. Really nice work! I look forward to seeing more!:)

Wow that was a long comment =) And you actually gave advice unlike lots of people lol. Yeah, I don't like it either really.. And it annoys me when I rhyme you with you lol. But that's how the poem turned out, and if I change it then it just won't be the same.. I dunno.. Thank you heaps though =) xxx