Which object is extremely useless, but you just can‘t get rid of it because it reminds you of something?

This is a wristband from a festival that I went to in Amsterdam this year. It reminds me of the fact that the organizers accidentally gave me and my friend
the guestlist and we were first super excited about it. But in the end, it turned out that we couldn't make any advantage of it at all. But still, it was a nice day and I wanted to keep this little object because it will remind me of everything that happened on that day.

Antonia, 23