John,
My father passed away from brain cancer when I was 14 so I (like many others here) know where you are coming from.
I'm not a religious person by any means but someone told me something once that I think relates well to situations like this "God took your (loved one) beacause he knows that you are strong enough to handle it."
That is probably not what you wanted to hear, but it has served me well thoughout my life thus far.
-Pete
