Bryan,
You never really lose them they just move on into a greater presence that we cannot see or touch, however when life tosses you a curve and things are tough for the moment that's when you'll feel them the most and know they are always with us. Take comfort knowing he is free from his physical pain and that one day we all shall reunite with our loved ones. I miss my Dad (age 68 due to cancer) and the conversations we shared, it's been 5 years now but I can tell you he has been with us and still doing for my family in ways I can't even begin to understand. It's okay to grieve, it's ok to cry and remember it's okay to move on and live for the present.
Sorry for you and your family's loss. Time will heal all wounds, try not to be sadden by the days you don't see him any longer but be gladden by the days you have had with him.