@Feistywoman, a wise soul here once said that "guilt should be reserved for when you have willfully, and willingly, done something wrong with intent to harm," or something similar. So, reserve guilt for really bad things (murder? cheating the Inland Revenue?) and don't let it in the house otherwise!
That was a bit tongue in cheek, but I do think that as carers, we are overwhelmed all the time, by physical caring demands, chasing paperwork, dealing with finances, sorting solutions to ever-changing issues, trying to live our own lives, and a lot of emotions, all the time. I know for a while that every emotion I experienced (a combination of anger, sadness, grief, bewilderment, and a lot more), felt to me like guilt. I kept thinking that I was doing something wrong, that if I could just get it right, things would be better. That was not how it worked out for me, because it turns out I wasn't doing anything wrong, it was the dementia making everything impossible.
We have a special pointy stick here on TP that we use for poking the Guilt Monster with. Perhaps someone would be kind enough to hand it to you? Again, this is all figurative and may seem a bit silly, but you really don't have room for guilt and it will not be helpful. It is so easy to say, and so hard to do, but please do try to let go. And go to your yoga class!
Dementia will take all the time and energy and emotion you can throw at it, and be greedy for more. It's an insatiable disease that sucks us all in, like a black hole in a bad science fiction film. Don't allow yourself to be consumed.
As a practical matter, it's hard to wrap your head around, but "normal" conversation and chats and logic and reasoning don't work well with dementia, and many of us find that we have to not do that any longer with our person who has dementia. It is counter intuitive to do this with an adult who appears normal and functioning and who has been an adult all our lives, so to speak. I often think the best training for dealing with dementia would be dementia education along with a combination of acting and improvisational comedy classes. It's very hard to adjust our expectations and our actions accordingly, to deal with dementia. It's even harder with certain types of dementia, or earlier in the disease, when memory and reason aren't so impaired and the person can have a sort of fluctuating level of ability.
There are some helpful "compassionate communication" documents available, if you've not seen those, and they are a good place to start. Generally speaking, don't argue, don't contradict, don't use reason or logic, keep explanations and comments simple and short, and when you find something that works, rinse and repeat as necessary. Distraction and diversion are also often necessary. It takes a lot of trial and error, and often needs adjusting.
None of this is easy and I am so sorry you are in this situation. Very best wishes to you.