The source material for this talk is taken from the Reasoning Book under the heading "Life".
In a nutshell, here are the points this material makes:
1. That it is essential to recognize divine authority and that we have a creator.
2. Life should be according to God's purpose, not ours.
3. Life is miserable because we have inherited sin.
4. We'll only be happy if we listen to God.
5. If we do the above, we can hope for a better life.
Unfortunately, none of these points answer the question! Perhaps what they are getting at, without actually coming right out and saying it, is that the purpose of this life is to be slaves for God, and hope for a better life next time around. This is not what The Bible says, anywhere that I am aware of.
However, the book of Ecclesiastes takes a very reasonable position regarding all of this. For its writer, this life was all we have and we should get the most enjoyment from it that we can because when we die, we are done. That's it. No where in that book will you find mention of an afterlife. (Ecclesiastes 9) We die, our memory goes, and that's it, gone forever. Seven times he says that we should enjoy life to the full as a gift from God because it's all we have:
"Look! The best thing that I myself have seen, which is pretty, is that one should eat drink and see good for all his hard work with which he works hard under the sun for the number of the days of his life that the true God has given him, for that is his portion. Also, every man to whom the true God has given riches and material possessions, he has even empowered him to eat from it and to carry off his portion and to rejoice in his hard work. This is the gift of God." - Ecclesiastes 5:18,19 (See also, 8:15)
My two cents.