It will take many, many lifetimes for "us" to learn more about the universe and our place in it. It may also take ongoing evolution of our brains to be able to ponder things we are currently incapable of even conceiving. It may even turn out that our brain evolution has limitations that will prevent us from truly understanding.

Based on what we know so far, we are the only planet with sentient life on it, and quite a large part of humanity doesn't consider that we may be rendering our only home uninhabitable. If we're to feel sad, that is where need to focus our energies - how to ensure that our home continues to be habitable for generations to come, while we continue to probe the boundaries of our ignorance.