Absolutely wonderful!
I lov this poem. Greatly done. But you said you wanted critisism so here's some: :D
The last sentence is a lil too long. It makes the flow just stop being flawless. You can make it shorter for example this way:

You leave me like an old toy.
So sad and so alone.
I have to stop myself from crying.
From the beginning, I should've known..

..That you were gonna go.
I shouldn't have fallen so deep.
Oh why didn't I realise.
I wasn't something you wanted to keep.

It would be better this way I guess.. But that's just me.. :) Good job anyway! 4.5/5
Take care

I like this alot. I love it. really. It really explains how i feel right now. I love that last sentence. Beautiful
<3
L.C