"Imagine that you were on the threshold of this fairytale, so..." — Jostein Gaarder quote meaning

Imagine that you were on the threshold of this fairytale, sometime billions of years ago when everything was created. And you were able to choose whether you wanted to be born to a life on this planet at some point. You wouldn’t know when you were going to be born, nor how long you’d live for, but at any event it wouldn’t be more than a few years. All you’d know was that, if you chose to come into the world at some point, you’d also have to leave it again one day and go away from everything. This might cause you a good deal of grief, as lots of people think that life in the great fairytale is so wonderful that the mere thought of it ending can bring tears to their eyes. Things can be so nice here that it’s terribly painful to think that at some point the days will run out. What would you have chosen, if there had been some higher power that had gave you the choice? Perhaps we can imagine some sort of cosmic fairy in this great, strange fairytale. What you have chosen to live a life on earth at some point, whether short or long, in a hundred thousand or a hundred million years? Or would you have refused to join in the game because you didn’t like the rules? (...) I asked myself the same question maybe times during the past few weeks. Would I have elected to live a life on earth in the firm knowledge that I’d suddenly be torn away from it, and perhaps in the middle of intoxicating happiness? (...) Well, I wasn’t sure what I would have chosen. (...) If I’d chosen never to the foot inside the great fairytale, I’d never have known what I’ve lost. Do you see what I’m getting at? Sometimes it’s worse for us human beings to lose something dear to us than never to have had it at all.