How do you deal with caregiver burnout?

I'm really struggling recently with being my Dad's caregiver. He lives in a great assisted living group home, but I am the power of attorney and even though I have 2 older sisters I am the only one helping my Dad. He has always been difficult to get along with and my Mom, my Dad and my sisters made decisions that caused them not to have a relationship so it falls to me. My anger and bitterness affects my ability to be compassionate when I have to deal with him. I've talked to him about it many times, and it will get better for a while and then he goes back to being difficult. I've been having anxiety attacks lately too. I truly feel stuck, and I know the only way the responsibility will end is when he finally passes away. What do I do until then?