It's true, people drop out of your life. Either you drift apart, or there is a break up of some kind, or they die. When I was young I hadn't seen any of that yet, but now at 47 I have seen way too much. My sweet grandma was almost 92 when she died. She was mostly happy and positive all l the time, but I remember her saying that nobody understands her anymore, that all her friends are gone, all her brothers and sisters and parents and other family are gone. She was proud of me and her other grandchildren, but concerned about the state of the world she was leaving. I'm glad I helped her last years be more comfortable and happy. She was a really great person, maybe a little bit like your dad. When those people drop out of our lives, it is always far too soon, even if they lived a full life. We always want another year with those people, and we realize when they're gone how awesome they made the world. And then they make you want to be like them, and make the world awesome with your remaining time.