Loss of abilities is something people can relate to more. The "permanent" part is more important than the "injury" part. A small scar nobody could see was a horrifying thought to me.

It extended to the mental as well. The thought that I might not be able to learn every language in existence in the narrow timeframe before my mind "hardened" against learning new languages was horrifying as well. (Particularly torturous, that one, because languages were dead-last on my list of things I needed to learn -soon-. I recognize Eliezer's fear that he won't be done with what he needs done by the time he's 40 - but start those fears at age 7 and thinking it may already be too late and you might have some inkling of what my childhood was like.)