What memories? What memories

Suddenly,what kind of sickness is the worst?
I reckon that is losing memories.
The patient will not notice anything,
maybe he/she can get back all happiness he/she lost before.
But who is the saddest person?
Must be his/her beloved one.
It is too hard to imagine what is going to happen if it's really happened in my real life.
I am just thinking of this, I can't stop my tears.
It is painful while he/she won't remember you anymore.
It is much hard to accept the one who 's gone.
I am too selfish but I don't want this happen in my life or my family.
Please god ,don't do that please. I am begging you.