Life can be very cruel sometimes. The fate of Alzheimer's is cruel, but I think the fate of patients' caregivers is even more so.

I truly wish I could offer more than just sympathy. I live in dread fear that I will slowly lose my mind and not realize that I am slowly exhausting and killing my wife, whom I love more than anything on earth.

If you have belief in a higher power, perhaps that can help you. During the darkest times of my stroke recovery, when I was in so much pain I couldn't stand it, I would recite "Not my will but thine be done" --- a lot.
It helped me to endure circumstances that I could not begin to comprehend.