This is a lovely write. It, I don't know, gets to me, like no other write you have written (okay, that's a lie, I do like many of your other poems too.) but this is also really good.
Haha... already improving I see *wicked smile*
I found this to be something many can relate to from the opening lines. So often we hide our pain behind a smile that others never really notice what's really going on behind it. This if further enforced when she then asks "why, " as it's something very commonly asked when suffering through pain and grief and when life becomes too much for us.
The closing lines are somewhat haunting, when mentioning she is now fading. It's as if she's finally had enough and no longer wishes to fight back; she's giving up hope. The only minor issue I had was that the flow in the last line seemed a little bit off compared to the rest.