No Reason

I just don't believe God takes people for a specific purpose.  I can't get my mind around it.  Some would say that I am a 'bad' Christian, I'm sure.  But there's no reasoning it for me.  I understand that He is All Knowing.  I understand that as humans we are supposed to struggle with our frailties and learn the lessons of life.  But I always feel like these things are random.  God set them in motion by making us weak, but He couldn't possibly want this awful life-changing sorrow for his children, right?  Some people don't recover from the seemingly meaningless things that happen to them.  I would have an awful time without my sister and husband, two of the most important relationships for any woman.  It would be crippling.  It just seems like too much.  The only thing that makes me think I could survive, is my son.  I'm just so sad for this family.  I'm trying to think of positive, comforting things; but I keep running up against my own sadness.  And I know it's selfish.  Why do we do that?  Is it another human frailty? This thinking of ourselves when a friend is in pain?  Or did God give us this trait so we could understand each other?  I don't think you can be touched by something like this and not appreciate your family more.  But that's all about me.  It doesn't help our friend.  I know there's nothing I can say.  I wish there was something significant I could do.