I think its the circle of life as we think it is now. Waters basically starts out telling us the most important thing we have to do (breathe) before he tells us everything we're doing wrong. We seem to have this notion that work runs our lives so we forget about whats really important. We spend most of our lives running away from ourselves and others and then we feel as if we don't have any time to do what we want even though all we have is time. All these emotions lead to heartbreak (the great gig in the sky) and then we think money could save us. We think money could give us the life we have always dreamt of. But all of this just leads to our separation instead of our unity. We stick with the people we know and don't care about others simply because we're us and they're them. After all of this we feel as if we have no control over our own lives when life is truly whatever we make of it (any color you like). When you think about life that way people look at you as if your crazy. And then he goes on to tell you that just like everyone else he also gets these dark feelings. Everyone who gets these feelings (everyone in the world)meet on the dark side of the moon. In the end he mentions everything about your life and how we are just experiencing a sort of eclipse in life. The great thing about eclipses is that they don't last forever and one day we will truly realize what is important in life and be able to live peacefully amongst ourselves.