Okay, the mending spell has fascinating metaphysical implications.
Like, imagine this scenario:
You have a beautiful rug in your wizard tower, but one day a bunch of adventurers come in to raid your place, and in the course of the battle a large hole, exactly one meter in diameter, is burned into the rug. Afterwards, you think about throwing the rug out, since the hole is too big to fix with a mending spell. But your grandma gave it to you, and the hole actually improves it in some ways, since you are able to put a round end table right in the middle.
So you keep the rug. Years later, you notice that the edges of the the hole have become a bit frayed in one spot, only a few centimetres wide. Can you cast mending spell to fix that frayed spot? Remember, that edge of the rug was originally created by damage to the rug that exceeded mending's ability to fix.