In Diane Rehm's new book, On My Own, she said something that really helped me. She described what it was like when she came home from taking her husband to live in his assisted living apartment:

"When I returned to our apartment at the end of that day, exhausted both physically and emotionally, I bowed to my enormous feelings of guilt and selfishness. It was as though I was standing in front of myself, screaming, "HOW COULD YOU?". And what could the answer be, other than "I had to. That's all there is to it. There was no other way.""

When I have to take DH to live somewhere else, I'm going to make a note for myself that says "You had to. That's all there is to it. There was no other way." And I'm going to read and reread that note until it sinks in, because it will be true. There is no other way. Even wading through guilt and feelings of selfishness (is it selfish to want to survive this yourself?) it's true that in our case there will come a time when there is no other way. Probably at some far distant point in the future there would have come a time when the truth of that sank in, even without the words in this book. But sometimes it's helpful to have someone else write down for you exactly the words you need to hear.