Uniquity
One thing I was not warned about before I got older was how it would feel to watch once-universal memories become more narrowly and narrowly shared, and once common cultural references become more and more obscure. As I get older, I realize more acutely that something irreplaceable will die with me. I find meaningful (though incomplete) solace in the thought that something new and equally irreplaceable, something that will be as loved and cherished, will rise up to replace it. Something always does.
The ubiquity of the unique. Uniquity.