So sorry to hear that Mike.  I know all too well exactly what you are feeling right now.  As Cavscout said, you did all that you could to do it well, and it unfortunately does happen on occasion.  

In my experience, if hit well, bears die quickly, and when the hit isn't so good they have a remarkable ability to recover.  From the description of your hit I am guessing there is a pretty good chance that he will be fine.  Get your head straight, and get back in the stand!

Mike
I hit the first Bear I ever shot at high like you described . I tracked blood for a total of 13 hrs, found his bed under a bunch of blowdown . I finally gave up and felt like crap for days, I killed that bear 7 days later coming to the cornfield I was hunting over, the wound was healing nicely and he was totally unaffected by it. Keep at it you just might see him again.