Yes, I understand. My father had vascular dementia and was also physically very frail - he had to be moved using a hoist for the last 4 years of his life. He died this January, having been ill for 9 years. When he first collapsed, I was devastated and in floods of tears. Over the years we had crisis after crisis. My mother looked after him (with help from carers) right to the end, but I remember driving South after the last crisis but one shouting to the world 'Let the poor old devil go!' But no - they patched him up and he struggled on for another 2 and a half years. His needs completely took over my mother's life.
By the end I was numb. For his final hospital admission, I was able to go straight to the hospital to support my Mum. We sat in A&E, waiting for someone to tell us what had happened this time (it was his second pulmonary embolism). We were chatting and calm - quite unlike the stressed families all around us. I did wonder at the time what the staff made of us.
Dad finally went out in style, with Mum, me and my two sisters sharing a 24 hour a day vigil by his hospital bed for the last 10 days of his life. (He was in a coma, and oblivious, but it was what Mum wanted.) By the end, I was too strung out to cry, or even to grieve very much.
But last month I was travelling in Asia, and went up into the hills. It was my first visit to the area, and I was fascinated by the land use and plant species I could see - an interest I got from him, along with our shared love of Asia. And I realised how much he would have enjoyed the day.
I think with these long drawn out terminal conditions, you do your grieving little by little as the illness develops and gets worse. Add to that the continual low grade stress you are under, and it seems to me that pretty much any reaction will be completely normal.