Numb

You may cause me pain once, you may cause it twice
And even if you try, I will not pain thrice

For you'd be trying in vain, trying too hard
Myself, I am precious, I'm always on guard

You may lie and shriek, give any reason to believe
But this crochet of trust is bloody tough to weave

This trick is for the smart, not the dumb
It's no more pain, if it's made you numb