Living creatures capable of reflecting on their own existence are a one-off, freak accident, existing for one brief moment in the history of the universe. There may be life elsewhere in the universe, but it does not have self-reflective consciousness. There is no God; no Intelligent Designer; no higher purpose to our lives.
Personally, I have never found this possibility particularly troubling, but my experience has been that most people go to considerable lengths to convince themselves that it is otherwise.
I think that many people find the suggestion dangerous because they see it as leading to a life devoid of meaning or moral values. They see it as a suggestion full of despair, an idea that makes our lives seem pointless. I believe that the opposite is the case. As the product of that unique, freak accident, finding ourselves able to reflect on and enjoy our conscious existence, the very unlikeliness and uniqueness of our situation surely makes us highly appreciative of what we have.
Life is not just important to us; it is literally everything we have. That makes it, in human terms, the most precious thing there is. That not only gives life meaning for us, something to be respected and revered, but a strong moral code follows automatically.
The fact that our existence has no purpose outside that existence is completely irrelevant to the way we live our lives, since we are inside our existence. The fact that our existence has no purpose for the universe — whatever that means — in no way means it has no purpose for us. We must ask and answer questions about ourselves within the framework of our existence as what we are.