Continuing the argument that our existential condition makes more sense if theism is true than if it's false we might consider our longing for justice, a longing for which there's no fulfillment if death is the end of our existence.
We yearn to see good rewarded and evil punished. Our hearts break when evil appears to triumph over good, but it's the common human experience that many good people live lives filled with terrible fear, pain and grief and then they die. Meanwhile, many who were the cause of that suffering come to the end of their lives peacefully and content after many years of pleasure.
In a world without God everybody comes to the same end, everyone vanishes, and there's no reward or punishment, just nothingness. In the world of the atheist, it ultimately doesn't matter whether you're Mother Teresa or Adolf Hitler, and there's no hope that justice will ever be done.
Another aspect of the human condition, of course, is the craving of a meaning to our existence. We can't bear living a life we know to be pointless and insignificant, but death nullifies everything and renders it all nugatory. In the absence of God there's no fixed purpose or value to anything we do. Some day the earth will burn up in a solar explosion, and there'll be not a trace that humans once existed. What will all of our striving matter then? All our efforts are like the furious running of a gerbil in his wheel. Our lives are just a footprint in the sand at the edge of a space-time surf. When all is washed away and the cosmos is left as though we were never here, the greatest acts of heroism, charity, and scientific discovery will mean absolutely nothing.
Consider these depressing reflections:
"Life has no meaning the moment you lose the illusion of being eternal." Jean Paul Sartre
"In all of our searching the only thing we've found that makes the emptiness bearable is each other." Contact
"If death ends all, if I have neither to hope for good nor to fear evil, I must ask myself what am I here for...Now the answer is plain but so unpalatable that most will not face it. There is no meaning for life, and [thus] life has no meaning." Somerset Maugham
If the atheist is correct, if our existence is simply a temporary fluke of nature, a cosmic accident, then we have no reason to think that anything we do matters at all. If, on the other hand, we have been created by God we may assume that He had some purpose for making us. We may not know what that purpose is, but we have a basis for hoping that there is one. Indeed, if there is a God (and only if there is a God) then we have reason to hope that what we do is not ephemeral, it's eternal, and that each life has an everlasting meaning.
RLC