Without faith in God, there is no way to find direction or purpose in life. Loving God, serving God, and knowing the word of God is what makes life worth living. God tells us to love others as he loves us. If we all followed that truth, the world could be a paradise. But selfish motives and lack of faith get in the way.
People think they can do it on their own, without divine guidance.
All of creation proceeds according to a great and beautiful plan. There is no way we can understand that plan, and to act without understanding is to act blindly. We need light to find our way. Of course, we are only human. Even the best of us loses sight of the path and falls.