I'm so sorry, I'm the least suited person to comfort you because I never met my grandparents... You know my parents got married very late, indeed I think I'll soon lose them compared to my peers. And this is also why I didn't have time to meet my grandparents. Only the grandmother on my mother's side was alive for some time, but she had a mental illness and I couldn't get attached to her…
Whenever someone expresses their sadness to me for the loss of their grandparents, I feel like I'm out of place, like when a woman says she's pregnant to someone who's never been. I know that grandparents emptiness is something that will never be replaced by anything, and that's exactly why I would simply like to tell you to keep all, absolutely all the memories you have of your grandfather, and to be happy of the life he lived!
It's true, life is infamous, but the good things it gives us are much more than the bad ones. And having the chance to spend a part of your life with a wonderful person like your grandfather was a great gift, don't you think too? Now he's gone, but we can't know where he's gone! Death scares us because it's unknown to us, but whether you're an atheist or a believer, no one knows what's after the death.
And you know what? It doesn't matter! Because your grandfather is alive in the hearts of all the people who loved him, he is alive in the moving memories of all of you.
Human beings are fragile, we are grains of sand in a large universe, yet they have the immense power to give love. And it is precisely love that makes us alive, and immortal in the hearts of others.
Take your time to grieve, vent if necessary, be sad as long as you like. And then stand up and show your grandfather that you will make your life the greatest adventure, just as he would like! Our losses remind us that we must live for them too, I'm sure your grandfather is in peace