According to scientific evidence, our existence as living beings requires the right mix of chemical ingredients and "Goldilocks" conditions inside and on the surface of our planet and in the surrounding cosmos, e.g. "just right" surface temperature, atmospheric conditions, the distance of Earth from the sun, etc. (And speaking of our sun, there is really nothing special about it. It's just an ordinary star on the edge of the Milky Way and just another face in the crowd, indistinguishable from the billion or so other stars [some of which may also have inhabited planets] that populate our galaxy and from those in the billions of other galaxies in the cosmos; so much for the notion of the world's and man's special place in creation).
Despite the staggering odds against the above mix of circumstances serendipitously coming together, this extraordinary convergence of events did happen. Thus life in its simplest form began on our world. And, as a result of the path that evolution happened to take once life did start, humankind is here to tell the tale. All in all, the whole thing is pretty amazing.
Yet in a sense life is abstract and is not the same as being alive. Although humans are hardly even specks against the backdrop of the universe, as sentient beings we have to ask ourselves what it means to be alive and have awareness, i.e. to look outward from the inside of our minds. However, we have nothing against which we can compare existence. There's no evidence of life after death or for past lives through reincarnation prior to the time of our conception. So when we say that it's wonderful to be alive and that we should be thankful for being born; well, being born and alive versus--what? Nothingness? If that's the case then had we not been born, then how would we know the difference? And when we die, we will return to oblivion, most of us to be eventually forgotten.
This is not to trivialize love of life or the survival instinct that drives it, just to put matters into perspective. I believe that while we are here we should try to enjoy ourselves constructively, enrich our knowledge of the world around us, and seek an understanding of the human condition. I further believe that to achieve these ends, we need to reject such shallow values as greed and materialism. After all, the thrill that many people derive from acquiring and possessing things won't add even an extra second to their lives.
Of course, theists, especially the fundamentalists, have solved this the issue of man's insignificance by inventing a god who they insist brought the universe into existence, created man in his image, gave us life through reproduction, and a soul which will be taken to an eternal afterlife when we die. They will not listen to evidence to the contrary perhaps because they cannot handle the concept of a world without a supreme being pulling the strings. It would be tantamount to jumping into an abyss.
Despite its limitations, the great thing about our existence is that no two humans are identical. We are of course individuals. As such I believe that it is incumbent upon us as a society to ensure that people's basic needs are addressed so that each of us can flourish and be productive. By doing so we can celebrate life even as we acknowledge and accept our role as bit players in the eternally unfolding pageantry of the universe.