I don't understand why you believe this thought exercise leads to despair or unhappiness. I went through this thought experiment many years ago, and the only significant impact it had on me was that I evaluate risk very differently than most people around me. I'm no less happy (or more depressed at least) or motivated, and I experience about as much despair as a non-secular optimist: occasional brief glimpses of it which quickly evaporate as I consider my options and choices.

And, to be honest, the process of looking at existentialism and going through some of the chains of thought mentioned in this article definitely improved my young adulthood. It made it more interesting and exciting, and made me more interesting to other people.

In any case, despair is not such a bad thing. Look at Woody Allen. Is he a joyless unproductive fear-ridden hermit? uh, no. But he's certainly thought through everything in this article, and accepted it, and turned it all into a source of amusement, curiosity, and intellectual stimualtion.