Depressing....sorry

I found out last night that my Grandfather, the only one I have left, is not doing so well. I don't understand all the technical stuff that was said to me, but it boils down to his heart, it's just not working as well as it should, and I don't know how much they can do for him considering he is 85 and has already had quadruple by-pass surgery.
He has said that he does not wish to be a vegetable, and that if that happens, please to just let him go...I understand that. He is a very active man, he, up until now, has lived on his own and still continues to go fishing in the spring and summer.
He lost his wife a very long time ago, my Nanny, when I was around five. He has been with some women since then, I do believe he cared for them, but I don't think he has loved anyone like he did my Nanny. I think this is why he has stated that he is ready to go, if it's his time.
But damn it! I am not ready for him to go....I know that selfish, but I am not! I don't want to loose him! He is my only surviving grandparent, and I don't want to loose him, I also don't want my kids to grow up without knowing him. My Oldest will remember him, as she is eleven, but the younger two won't, and it just doesn't seem fair. He is so good with my kids, always joking with them and making them laugh...he always picked on me when I was a kid (teasing...the good kind) and I don't want my kids to not get a chance to experience that!
I don't want my Mother to not have either parent left, I cannot imagine that pain...I cannot imagine not having my parents, I just can't, I know they say you move on....but I don't think I would ever be the same, and I know she won't either. Her and her father have come a long way, and I know she is not ready for this either....
The whole thing just sucks. I hate it. I hate that it is happenning, and I hate that I feel this torn, I don't want him to have to live in a way that does not make him happy, but damn it, I want him around! I really hate this, I really do.....
I don't know what else to say, thanks for reading this....thanks.

Love,
Katie.