at my wits end

My husband has stage 4 pancreatic cancer and I don't seem to be able to motivate him to do anything. I understand that it must be terribly hard to be told you have cancer and cannot be cured. I am trying to motivate him to get even a little exercise but he just says it's not time, he is too tired. He was my caregiver 7 years ago when I was diagnosed with lung cancer. Fortuneatly I was able to have surgery and was cured. We have different attitudes toward life. I see the glass half full and he sees it half empty. I just needed to vent to someone who understands. If anyone has any suggestions how I might be albe to get him out of his funk I would appreciate it. It almost seems as though he is giving up. 

Thanks for listening.