Having my mental state degrade.
Anything that would mean that I am not the same personality I once was.
The whole not being able to hear, see, be as active, be as attractive, or have the same hand-eye coordination. Doesn't really scare me.
But the prospect that my mental capacity may degrade, that my memory may be lost, or that my personality may change all together. Is something that really does frighten me.
It really does unnerve me that in just a few years my mental state may degrade to the point where I'm a shadow of my former self, and that I may never remember the days when I was better.
It makes me feel vulnerable to think that all the memories that I now know.
From common knowledge about math, science, history and life
To the faces and personalities of my parents, my brothers, my sister, and my closest friends.
Could all be forgotten, not by others or by some outside influences, but by me.
It hurts to envision that I could unknowingly loose a grasp on everything I hold dear.