The scary thing is that we can't understand what it feels like to have Alzheimer. Once progressed you become unable to judge the situation like you are used to. The world looks different from a patient's perspective.
Having worked in a nursing home, the outlook someone with Alzheimer's has in not pleasant. It's confusing and, in the early stages, you're aware of everything you love and the understanding of your place in the world slowly slipping away.
It's not some peaceful slip into senility and oblivion... it's more like a sawtooth graph of waxing and waning awareness, punctuated with extreme frustration, and terror.
I've only had contact to patients experiencing the calm phase. It must be hell slipping in and out of consciousness and realizing for a short moment what is happening until it vanishes again. It's stuff for nightmares.
I know what it is like to have lost a favorite book and look for it in vain for days before the love wears off. If I had that feeling every day, just the feeling alone would cause my mind to break down. Ever remember having a great idea, but not remember what the idea was?