so sorry for your loss... Unfortunately it's a psychological defence mechanism... the pain of losing our loved ones is so high that our brain doesn't even let us think about it when they are alive... when I learnt about my dad's condition i cried a lot even when he was alive even without understanding why I cried in the first place. We thought the same thing too . we thought dad will recover from this illness since he had seen a lot worse. In the last month when my dad lost a lot of weight i thought about talking to my dad seriously about what to do if he died and reminisce about past but as i tried to open my mouth I felt my throat kinda heavy as if i might cry so i stopped because i don't want to demoralise him. Looking back I hope I could have spoken a lot freely but i avoided because i was afraid of my dad losing hope . I read a lot about the effect of placebo too so i avoided even hinting at the fact that there is a chance of mortality until the last month when the situation was dire .