My Mom has been living with me for almost a year. She is 96 years old and has slight dementia. She cries all the time even though the Geriatric Doctor has changed her anti-depressant a couple of times. She also says constantly that she wants to die because she can't do the things she use to do. She is physically healthy but uses a walker and wheel chair. She says thing that upset me and I usually wind up crying. (Maybe I'm too sensitive.) I know she doesn't mean to hurt me but sometime she treats me like I'm 12 years old. If I go to the store she wants to know why I took so long. If I go to my room she'll talk to herself and say "I'm all alone again. She leaves me all alone." She complains that no one comes to visit her when she has company almost every day. Her grandchildren and my brother and sister come over frequently. If I tell her they were visiting her this afternoon she tells me that was last week. She doesn't remember that they were here. Then she'll get depressed because she feels all alone. I feel so bad for her. I hate to see her so unhappy. .
Don't say, "Mom, you have so much to live for!"
Do say, "Oh, Mom, you're so lonely and sad. I love you, but you are still not happy. It feels like you're all alone, doesn't it? It feels like you have lost everything, You used to be so strong, You could go anywhere you wanted to. Now you're stuck in this rotten wheelchair. Of course you're sad." Use this when she cries, and use it when she verbally lashes out at you, because she's sad then, too.
Let her know you UNDERSTAND why she's not happy. Face it, it just plain sucks to be her. It would suck MUCH more without you, but it still sucks.
Human nature being what it is, If you tell her all the reasons she has to be sad, she will just naturally be forced to contradict you, by admitting that it could be worse. But she has to be the one to say it.
We always think we should console the sufferer, but the first step should be to acknowledge their suffering. Offering solutions and pointing out the positive both come later, if at all. IMHO.
Hugs to you both.
Like others have said, you're doing a wonderful job and since you don't control the universe (don't we wish!), you can only do what you can do to make your mom happy. Her brain isn't right, so there's only so much you can do to help. Hugs to you and your mom.
Hang in there!