God must exist, you see. He just has to. Otherwise the quality and beauty of life is cheapened.
If--and this we cannot prove--God does not exist then we have to become our own all-loving, all-forgiving and all-comforting "God."  Let us not even consider the quagmire of dealing with lower-case gods or beneficent forces of nature. We need God or the ideal implied by the word God, not just for each other's sake, or for our own sake. We also need God or the ideal of God ("God") for the benefit of the culmination of eons of evolution--pre-primate and primate--as well. Ultimately we need God if only to insure that our own health and survival as a species is assured for whatever fate or providence or some nameless and undefined Factor or Ideal has in store for us down the road. Without something larger than ourselves millions of years of human evolution lose whatever meaning artists and poets have attributed to the wonder of being human and being alive to enjoy that splendor and glory. 
Humanity really, then, is created in the image of God. We are carbon copies of our perfect and wonderful God. We need God, however, to let that wonder and perfection shine and grow. Not from within ourselves only but from a mysterious reality or force beyond ourselves. That mystery can only be called God. It truly can be said of us, His children, that "we are the light of the world."
- It may not be necessary for some, but in the event that there is some confusion as to what I'm referring to when I speak of God (the deity of the Old and New Testament Bible) and "God" (the ideal of God or a conceptual God, if he were not to exist) this note may prove helpful. Again, it is not my intention nor concern at this time to address any interaction or use of a lower-case god. There are already too many lower-case gods in our postmodern world.
- Though probably used in a different context and possessing different meaning than what I've presented here, I am partially indebted to Jack Provonsha's "God is With Us" which I read at the age of 19. It still lingers in my mind though only vaguely. It was there that I first came upon the sometimes confusing uses of God and "God."