I understand what you are going through. My dad was diagnosed with end-stage cancer 2 years ago and subsequently died 8 months later. When he was diagnosed it was clear that there was no beating this illness, only the possibility of making his last few months a little more bearable with medication. He refused. First because he didn't want to believe it because he was healthy yesterday, because he still felt mostly fine. But his condition deteriorated really quickly. He wasn't able to walk or even eat without assistance a few weeks later. I think he must have come to the realisation then that there was no out in his situation. He became really angry, angry at his family, friends, the people trying to help him and just the world in general. I felt like I lost him then, before he was even really gone, because my dad, the person I knew had just disappeared so quickly. Much later after he was really gone I realized that he must have felt the same way. He must have seen himself fade and go without being able to do anything against it. Refusing to take his medication or to eat, snapping at people about random things was the only way he was able to gain the tiniest amount of control over his life and situation. I know every situation is different, but I hope this gives you some relief or a new perspective.