Picking up your things and leaving in a huff is never the way to go. It didn't work in kindergarten and it won't work now. Sagittarians don't always take criticism well (you're worse than Leos) and you often react as if you've been personally singled out. Nevertheless a loved one won't back down which begs the question: is it so hard to say that you messed up? People mess up all the time without making such a big deal of it. Yes, the truth hurts, but you'll never improve if you don't listen to what needs to be said. Besides, it comes from a good place.