 About the earworms, I get them regularly and when I'm feeling good, I can switch them like in a jukebox when I've listened enough to one song. But when I'm stressed, the tune sticks in my head and when I'm really stressed out, the piece that is in the loop gets shorter and shorter. Then trying to switch to another song doesn't help because it comes back until I do something about my stress. So earworms are a good indicator for my well-being.