A metaphor from middle school

I don't actually remember when exactly this thought comes from, but in school, as a kid, I had a tendency to draw on and poke holes in erasers with a pen. This of course turned the eraser into an ugly mess, which it was impossible to fix. I would then be struck by the fact that some things, once ruined, never heal or grow back. It's actually kind of weird how vividly I remember that feeling, especially considering how little else I remember from before high school.