Age filters

What happens when we age, why do we change? What part of ourselves do we lose, or is it more a case of we lose that which isn't essentially us.

Mental acuity is an important part of who we are, I know that when I get older the possible loss of being able to think and work out stuff for myself scares the living daylights out of me. I can't imagine being myself if I couldn't express myself as well as i do now.

I see old people struggling with concepts and ideas that they must have coped with when they were younger.

I see them react as if they no longer have filters to moderate their behavior.

So, have they lost or found themselves?