How to deal with feelings of guilt, for putting Dad in nursing home?

I have been caring for my dad for 7 years in my home. He had 2 strokes and was unable to live alone. over the years he has developed dementia. I needed respite care for him to take a much needed vacation. took him to nursing home, very next morning, was called to come and get him because of his disruptive behavior. He had never displayed this kind of behavior before. Finally found nursing home with a dementia unit,(wonderful place), he had behaviors there, combative and would not cooperate, the facility is trained for these types of behavior with dementia. I did get a short vacation thanks to them. upon bringing dad home his behaviors continued, unfortunately, I had to face the fact i was not able to continue care at home. My dad is 93 and i am 60 , we have always been close, and this was the hardest thing in my life to do. He is back in the same facility , doing ok so far, except when i go see him he gets upset, and says why am i here. The guilt of having to do this is tearing me up, how do i get through this? I put myself in his shoes , no family around, dont understand why im here, sharing a room with a stranger, missing the little dog. I cry everyday thinking about this situation. Please help.