So sorry to hear this anon. My grandpa died back in December 2019.
I hope you can spend some time with him before he completely passes. That little chance to say goodbye can be so comforting.
I was fortunate enough to be able to have a special goodbye with my grandpa, and I think it's the sole reason I was able to cope so well.
He was like a second father to me, as that set of grandparents lived across the street from me when I was little.
Grandpa's get to be this major pillar of the foundation of a lot of families, especially big ones like mine. It shook us big time to lose him. The night before the funeral, we decided to have an old-school style wake. We didn't have the body for viewing at it, but we got the whole family together in one big room to sit around and tell stories. An old pillar of the family like a grandpa will have hundreds of stories surrounding him. As horrible as it was to lose him, that wake was the best part of the whole ordeal. I'd encourage you to do the same with your family, if you can.
The spirit of him is still always there, whenever we get together. He's never far away.
He'll be alive as long as you keep him in your heart, and all that other shitty sappy grief stuff everyone likes to say.
If there's a heaven, I hope he has a great time there, and I hope he'll continue to look out for you, and help give you a sense of guidance in life.