You

Check your six
When you walk your path
For on your heels, I shall haunt
And as you stop to gleam
Per chance upon a gentle moment
I shall only place upon you my gift of hurt
Yet only for to know
If you are indeed worth your salt
And then I will punish you worse
Till you keep up the fight
I am not your enemy
I am you, your own
I am the sentience in you
The one that lets you never be happy
For you are my clay
And I am your klin
You will be transformed by me
Yet you will always want to fall and break