MaJoC's Musical Aphorisms:

The music you recognise out of the corner of your ear will date from when you first started thinking you were a grownup. After that, most people are too busy actually being grownups to lay down those memories.

Everybody's middle-aged inside their own heads. Once you mention some singer or group that everybody knows about, and the youngsters say "Who's that?", *then* you realise you're old.

Full disclosure: I've been saying "I'm young for my age" for so long that I now should add ".... but with an increasing range of physical annoyances that slow me down".