Hi Diane,
I was a caregiver for my father when he had terminal lymphoma and it was one of the most difficult seasons in my life. I spent a year in therapy over it. Now I am a cancer patient myself and my wife started therapy today. A big part of this disease is that is simply overloads everything, whether you are the patient or the caregiver and it's very stealthy the way it does it. I have learned to cope by staying in the "now" and trying to avoid thinking about the future. And like Joanna said, you need to take a little time for yourself each day also. Caregiver support groups can be helpful also.