Justine,
Just so we're clear -do you believe in life after death?

In response to your post, the fact that people wouldn't 'turn back time' to undo their suffering is only because they have adapted to their new life. When you get the news that a family member or close friend has died, I doubt you will not-be wishing it hadn't happened. Perhaps in the future, when you have coped with the issue, you would wish not 'go back'. This is because going back would be the equivalent to suicide -you'd be erasing your life! Obviously no one would want to do that!