Answer:
Walk on the living, they don't even mumble. Walk on the dead, they mutter and grumble.
Slayer of regrets, old and new, sought by many, found by few.
It doesn't live within a house, nor does it live without. Most will use it when they come in, and again when they go out.
My first is twice in apple but not once in tart. My second is in liver but not in heart. My third is in giant and also in ghost. Whole I’m best when I am roast.
One by one we fall from heaven down into the depths of past, And our world is ever upturned so that yet some time we’ll last.
Keep doing me to avoid lens dryness