"He was her everything and she was his
Even though he was unaware.
Everyone could see it, it was right from the start
But that boy couldn't just look at the heart.
He wanted a beauty though they had hearts of beasts"

Good opening that explains to the reader all that is going on.

"She stood by him and he beside her
She told her girl friends i cant take it anymore
He asked his guys whats she complaining for
Her friends would smile and say he'll figure it out soon
And His buddies would shrug and say Frisbee at noon?"

I felt the rhyming here to be forced, and this in my view was a very weak stanza. Here are my suggestions:

First line: Good, nothing wrong here.

Second line: "i" should be capitalized, proper grammar. "cant" should be "can't".

Third line: "whats" should be "what's". A question mark should be added at the end of this line.

Fourth line: re-write to this: "And his buddies would shrug and say, "Frisbee at noon?".

You had some things mixed up in that line, so it needed to be cleared up.

"When he met a new girl her heart always sank
She never met boys maybe his would've too
If only life was a story like this
That every time would end with a kiss
But this one is different it ends with the slit of a wrist "

The flow was very rocky here, in the last line, shorten some words to make it a bit better.

Second line: This doesn't make sense when I read it, try rewording it for better understanding.

Fourth line: Change to this: "Where everyday would end with a kiss". It reads and flows better.

Last line: This also felt forced rhyming, its a love poem, so it ruined it for me that cutting had to be in it. I just thought it was not a good way to end it, use more emotions and creative images for the reader.

3/5 from me. I also noticed you used no punctuation, it really helps the reader and looks much better. Just my suggestion, but its good to use it.

Take care and keep writing, always and forever...

~MaryAnne

Sorry, I forgot to mention something else. One main reason I voted so low was because of all the filler words. It really gets boring when "she" and "he" are repeated so often, just be creative and unique.

~MaryAnne