I keep thinking about how much time I (and my family) have left

None of us have any terminal illness but every day passes, I see my mom gets older and older, I fear that one day I will wake up and I won't see her eating breakfast, one day when I come home, I won't see her at home, and I can't help but feel terribly sad thinking about it.

My grandfather passed away some years ago, I still miss him to this day. I think I'm the kind of person that can't deal with loved ones passing away. I don't know if I could deal with it when it's my mom's time.