Scared of losing people

I (M21) am scared of losing people in my life. And at the moment it’s my grandfather, now nothings wrong with him that I’m aware of, he’s still active and 75, but again he’s 75 so getting up there. I didn’t grow up with a dad so I spent a lot of time seeing him in my childhood, I would fly down and see him a fair bit and it was great. Only now that I realise he’s old I’m scared of him passing and more so how I’m going to handle it? The thought of it does make me cry and upsets me, I do realise it’s a fact of life but I just want to be able to keep it together and not fly of the rails. This is the same if my dad who’s not in my life goes or my mum. I just wish there was some mental preparation for these type things.