This is time for us. Memory. A nostalgia. The pain of absence. But it isn't absence that causes sorrow. It is affection and love. Without affection, without love, such absences would cause us no pain. For this reason, even the pain caused by absence is in the end something good and even beautiful. Because it feeds on that which gives meaning to life.
Our moral values, our emotions, our loves are no less real for being part of nature, for being shared with the animal world, or fore being determined by the evolution that our species has undergone over millions of years. Rather, they are more valuable as a result of this: they are real.