Life here is first and foremost arbitrary. As a result of this, the world is like a blank canvas we look out to and fill in with meaning.
The life of a human can be wrought with meaningless acts that have been given a lofty value in the human's head. One human says "This is meaningless!" while the other calls it holy. Many take this as a lesson to say that happiness is found by arbitrarily assigning value, but this -- and all idols -- will fail.
The great lesson of this world is to find yourself. This is necessary because the world is a dream; a very complicated but simple illusion. How does one escape illusions? Surely not by fighting with them, but by letting them go. This is why monks train so long to let go of attachment to the world and learn how to disconnect from it. The enlightenment that follows is but recognition of the real world -- what some would call "heaven" or "nirvana".
Different strokes for different folks, but the end-goal will always be the same for this world. The "last judgment" will be when the world has finally been judged truly and we relinquish from it and go back home. It might be many, many years away, but there are some of us whose only purpose is to accelerate the return.
Therefore, knowing that I have a purpose, responsibility, and finite time on this world, the equation for what has meaning to me is "Is my function aligned with my purpose?"