My father has gone through the whole spectrum of personality changes - none really, have been easy. For reference, he is now mid to later stages of Alzheimers.
Anger and Suspicion
This seemed to be earlier on, though Anger came up later as well. He always thought someone was stealing from him and so would hide things - random things...some to be honest we never found!
He would also get angry about it and a few times specifically got very angry at me directly - it shocked me. My father has always been even tempered. I did though become POA and was the one that had to tell him he can no longer drive (we had a test done so it wasn't 'me' telling him). He got very angry , calling the test bs and the instructor 'was out to get him'..etc. He even yelled at me when I was driving him to the Dr because I 'didn't go the right way'...he say "G-damnit, you're going to fk this up!". I have never heard him let alone yell like that to me - to my face before.
How did I deal with this? I stayed calm - honestly I was angry myself, but I stayed calm....I didn't respond, I ignored him. I don't know if that was 'right' but its what I did and it passed
Sadness
Anger was early on but so was sadness, and sadness still comes now in later stages. He will try to tell a story (from way way long ago, usually his childhood) then he'll say "theyre all dead" and just start crying. Or if I mention my niece's name and that she is coming to visit, he'll pause and start to tear up then say something about children....
He usually pauses just before he's about to go deep emotionally, and so I will try to change the subject. It's easier now in later stage but was really hard in the beginning when he could really tell the stories you could understand...
How I deal with it? Again, I would try to change the subject - talk about something else.
Frustration
In some ways, this emotion upsets me the most. At times I can see the frustration he has - with words, with his memory. Sometimes I can even tell he has a realization that he has this disease or that 'something is wrong with him'. It's hard to watch and be a part of - and it makes me the most sad; I can deal with anger and his sadness over lost loved ones, but frustration hurts the most. It's a weird form of reality of the situation, for both of us.
How I deal with it? I try to help him find the words he's struggling with, or just agree with whatever he says (I do that a lot), or ask him a different question. I don't know if those the right things to do, but its what I do.
My father is in a memory care home coming on 2yrs now and I still see him every week. I get stressed out when I go there and I always am sad when I leave, not sad for leaving, but sad inside from my visit. But he recognizes me and is genuinely happy to see me. That is what I focus on.