Aw hun I'm so sorry. ;_; I know what it's like to have grandparents pass (I only have 1 left..) indeed it's very sad you'll never see them again but celebrate the times you had with him. <3 I send my sympathies and love to you!
Do not become overwhelmed with your grief on his passing, but rather celebrate how he lived and shared his life with his loved ones, family, and friends. I'm sure he would have wanted to be remembered for all the great memories he left behind rather than how he passed away. It is through these shared memories with those who have survived his passing that his legacy shall live on in your hearts forevermore.