If you hunt from an elevated stand, practice, practice, practice from an elevated stand. You will still probably shoot over the deer's back. Then practice , practice, practice from an elevated stand. Then, you'll probably shoot over the deer's back. Then, practice, practice, practice, etc, etc, etc. I know I'm not the only one this has happened to.
Then don't give up. Because when you make that first shot, seeing the arrow dissapear right where you were burning a hole with your eyes, the flood of emotion is better than any gun or compound kill you heve ever experienced.
Focus on a hair, not the deer.