Particularly where you don't want to be mean to someone in real life about how annoying it is so want to get it out on here.
Example: It's lovely that my DM wants to help with washing up/loading the dishwasher, but lately I bought eight lovely bowls and a week later she knocked over four of them which smashed, and now I can't get the same ones to replace them as they are no longer available. I bought some more plainer, cheap bowls from IKEA yesterday and DH has already dropped and smashed one.
DM has also smashed one of my crystal gin glasses, one of a pair of crystal wine tumblers, and even years ago I had a matching set of six wine glasses for approximately five minutes when she smashed one in the sink. She isn't elderly and doesn't have mobility problems, arthritis or anything like that. A lot of her helping is just actually not helpful at all - fussing, fannying about and interfering and makes things more difficult for me.
Ok, everyone breaks things sometimes, I do all the cooking and a lot of the tidying and have dropped the odd plate over the years, but everyone else seems so much more disproportionately careless with my stuff. Stop being so bloody clumsy and breaking my stuff!