I think the fact that no one can predict who will get dementia makes it really scary. One of the patients I knew was a brain surgeon.
I have noticed before that some people try to blame someone for getting sick (they didn't exercise enough, or eat wrong foods, or they smoked, or didn't do enough crossword puzzles)---is a way of trying to exert control over their future. Thing is, when we blame someone else for getting sick it makes us feel better, but the patient feel worse.
Seekingtruth, you might be interested in "Who Ordered This Pile of Dung?" by Ajahn Bhram.
Okay bear with me … [Who Ordered This Truckload Of Dung by Ajahn Brahm!](https://www.amazon.co.uk/Who-Ordered-This-Truckload-Dung/dp/0861712781)
Before anyone else downvotes, this is an actual book
I can highly recommend you this book. Don‘t let the title mislead you. It is really good.
I also had a lot of unpleasant memories and depression when I started with Buddhism. My mind would automatically fall into the same ruts of anger and hopelessness--it was hard to sleep and i had to keep myself constantly busy so I never had time to stop and think. He's got a book of 108 short stories called Who Ordered the Truckload of Dung?. Those stories are short and catchy and helped me come up with ways to "answer" the negative thoughts and feelings.
He also has a lot of dhamma talks online--this is a list of his [most popular dhamma talks(https://www.youtube.com/user/BuddhistSocietyWA/videos?shelf_id=3&sort=p&view=0). If you're not connecting with one of the talks, just move on to another.
Freeing our Minds from their mental prisons was also really helpful. https://www.youtube.com/watch?v=Qg_FsPEwOB0
I have a laptop next to my bed. I would turn them on whenever I went to bed, so I had stuff to listen to while I was trying to sleep. I also would crochet stuff during the day and listen. Basically, I just bathed myself in his words until he "brainwashed" me into loving myself.
Eventually I got to the point where I had enough distance from stuff that when bad memories come up, I can think about them without drowning in them--so I do feel a lot more detached and distant from them. I can also pretty much choose when I want to stop thinking about bad memories--they don't control me.
I did all this in conjunction with cognitive behavioral therapy. I'd done therapy for years, but Buddhism was the key that unlocked the door.
Also, did you know about /buddhistrecovery?
I love his book "Who ordered this truckload of dung?" http://www.amazon.com/Who-Ordered-This-Truckload-Dung/dp/0861712781
Who ordered this truckload of dung? is one of my to-go books, though it's from a buddhist perspective so your mileage may vary.