From the few people in my life that I have lost, I have learned a few things. First and foremost is that saying of "Don't go to bed mad at someone" is so true.
I had a very good friend that was killed in a motorcycle accident in Jan 1999. In Sept 1998, we quit talking over what I really don't know anymore. We worked together in offices next to each other. Those times when we did talk in those 5 months is was just work related stuff. The weekend he died, I had decided to try to bury the hatchet, but never got the chance. It still bothers me, but I know we were true friends, just stupid shit that made our egos get in the way of sucking up our pride and saying "Sorry."
I lost my father when I was 16,and he was pretty ill most of my life, so I never really got to know him as much as I wish I could have now that I "grew up."
Like the others said, life goes on and we all deal with tragedy, I wish I could say something more helpful, but everyone deals with death in their own way. Though time may be short, make the best of it and cherish it, memories are priceless, relive them with him while you can.