Hello fallin,
Basically clichés are overused phrases. They used to provoke strong
emotions but now lost their magic.
Some examples are,
bitter end
cool as cucumber
hard as nail
drenched by light
burning heart
endless horizon
eternal sleep
grim reaper
shadow of death, etc.
If you used too many of them, your poem will become very boring.
The problem is some clichés are hard to identify because we are so
use to them.
Take your poem for example. Do you think there is anything new with
these phrases,
shattered pieces
fallen glory
unseen presence
bladeless knife
silent torture, etc.?
Not really right? 
By the way, want to share with us what youve read?
There are some links regarding clichés in the Introduction
thread, feel free to check them out. 
