You might become it, you might feel it, but you must never act it or, even worse, look it. This is especially true of the music industry where the way things were in the old days has been fatally undermined by young people who think a tune is something you download or rip off for free. But still the old musicians don't get it. Still they try to be like the young. Still they try to keep up with the people who are destroying them.
It's this phenomenon, more than anything, that will probably keep us interested in the new country music drama Nashville (More4, Thursday, 10pm) because fear of ageing doesn't apply just to the music industry – increasingly it applies to any career and pretty much any woman no matter what she does for a living. In Nashville, the victim is Rayna Jayme, a fictional country music legend whose career is on the slide.
"The way everyone talks now just makes me feel old," she says. She also doesn't like the sound of modern music either. "Why do people listen to that adolescent crap?" she rages. In other words, she's done that thing we all do – slowly, inexorably, like a Hammer Horror special effect, we are body-snatched by our parents and become like them: raging against modern music and how "is" isn't as good as "was".
The specific "adolescent crap" Rayna Jayme has in mind is the music of Juliette Barnes, another country singer who's much younger than Rayna and also, increasingly, more successful. If you like country music, you will recognise both these women: tiny little things sheltering in the middle of a creation of hair and jewellery and make-up and glitter.
All their songs, too, are randomly generated from the same four words: lonely, tears, blanket and geetar. One of Rayna's songs includes the line "crying black mascara tears" which is pretty much the perfect country and western lyric.
Not that Nashville is really about country music – in fact, it's just a soap built around a glitzy bitch-off along the lines of Alexis and Krystle in Dynasty, and it will be especially beloved by gay men for that reason. Some of the best lines ramp this up. "My momma was one of your biggest fans," says the young Jessica when she first meets the older Rayna. "She said she used to listen to you when I was still in her belly."
Such bitchiness aside, what is Nashville about then, if not country music?
Rayna's issues with ageing are certainly part of it, although there's also a subplot about the cost of success when her husband stands for mayor. There's also the suggestion, when a waitress is talent-spotted in a Nashville bar, that it could be about the American dream, although that's as fatuous as it's always been.
In the end, Nashville is just a fluffy, bubbly soap. A drama with a twangy country soundtrack and two stars: one old, one young. And could that be its fatal flaw? Could Nashville be too old for the young but too young for the old?