We find comfort in light. There is ample symbolism that gives light an undoubtedly positive meaning -- the light leading to an Afterlife, light as serenity, peace (have you ever seen any peace symbol that was surrounded by darkness?), energy, goodness.
But there is something better than light. It's the twilight; it's the knowledge that the light is there somewhere, it just needs to be found. The anticipation of light gives us hope and keeps us going.
In ancient mythology, there is a concept of Paradise Lost, mankind's fall from grace. But in my view, Paradise is not really lost. Man did not fail or screw up. Instead, Man was shown a glimpse of Paradise, and then told to earn it. Without seeing it in the first place, Man would never feel incentivized to keep looking for it.
In a way, what makes us human is our desire to keep looking. We are always aiming for the next great thing. Progress is just a disguise for mankind's search of answers to the infinite stream of questions. It doesn't matter how many questions are left. It doesn't matter where and when Paradise will be found. We'll keep looking -- that's all that matters.