throwing away something that has sentimental value. There seems to be a real aversion to the idea that this thing that has high emotional value is really just garbage. They cannot abide the idea of sending those things to the landfill, but they can allow themselves to part with the item as long as they believe that it will still be used (and loved) by someone else.
This happened over and over again when I was helping to clean out my in-laws' house. I just wanted to haul it all to the dump, because that would be fastest and easiest (it was going to be a big job, and I just wanted to get it done), but my wife and her sister would have none of that. There was much sorting, and several trips to DI (no appointment needed back then, thank goodness). Oh well. I knew better than to try to get into that situation, so I just made the extra trips.
I don't know how much I will do that when I'm cleaning out my own parents' house (I have no trouble throwing away my own stuff when I'm done with it), but I am fully prepared to deal with the same issue with my sisters. So at least I have that to look forward too. 🙂