The best advice I got when dealing with my father's passing was this: Don't leave anything unsaid. Good or bad, say it to him if you get the opportunity while he's still breathing. Even if you don't know he can still hear you. Once he's passed, a door closes forever. Tell him from your heart a favorite memory, what he really meant to you, what his life has meant to yours.

I hope your relationship with you wasn't as conflicted as mine with my father, but getting to say some things I needed to say to my dad gave me a closure that I needed in order to gone on. Visit him if you can, touch him, talk to him as openly as you can. It's the best way to be at peace with, and hopefully ease, his passing.