I'm so annoyed. >.< I just typed up a really large comment and then P&Q decided to go weird and delete it! Anyway... on I go again.

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Before I start, I feel I have to tell you that the stereotypical "emo poetry" relating to a theme of suicide/cutting kind of drives me up the wall. >.< I'm sorry, I just find the whole theme somewhat... overdone? However, I'll point out some specifics in your poem, because I believe that just because an individual does not like a certain theme, does not mean the poetry itself has to be bad.

"I sit here and I fake,
the smiles everyone sees.
I know that with this knife,
the pain will soon ease."

^^ Your first stanza here is a good example of why I dislike this theme of poetry. The whole "I fake a smile"/"I cut myself" is just so unoriginal now. I'm not saying this theme should be abandoned altogether, but it would be nice to see somebody put a unique spin on it sometimes... so their words aren't so... blunt?

"No one could ever know,
the reason why I hide.
I tell them that I'm fine,
but we both know I lied."

^^ However, in saying that, I actually really liked this stanza, especially the line '...but we both know I lied'. It adds a interesting confusion and the reader becomes intrigued, wondering who exactly 'both' are. It could be the narrator and a lover, the narrator and a friend, or even the narrator and a parent. I like that mystery.

Overall, it's not a bad poem. I just can't say I enjoyed it as such, but that's just my personal preference. :]