Answer:
I don't think or eat or slumber. Or move around or fear thunder. Just like you I look the same but I can't harm you or be your bane.
By Moon or by Sun, I shall be found. Yet I am undone, if there's no light around.
It comes only before, it comes only after. Rises only in darkness, but rises only in light. It is always the same, but is yet always different.
What can't you see, hear or feel, until its too late. What shadows love, and shopkeepers hate?
I have a tongue, but do not talk. I follow close, but neither run nor walk. Coupled and hitched, but never married. You couldn't bear the load I've carried.
you hold my tail while I fish for you