I believe in God.
But I was once an atheist. Well, technically, I was an agnostic with atheistic tendencies. What I mean by agnostic, is that I believed there was no way to know for sure whether or not a god, goddess, gods, or goddesses exist. So I figured, if there is no way to know for certain, that the odds were slightly in my favour for not believing.
As my life went on that paradigm was consistently challenged by the reality I was facing. The first crack in the foundation was the lack of purpose, and not just my own. If there was no God then there was no purpose to my life, your life, or anything. As I followed the logical implications of atheism, to things like purpose and morality, life became very depressing. If life lacks purpose then why bother continuing to exist Needless to say, I sunk into a heavy depression about this time.
However, I refused believe that the universe was some giant cosmic mistake. It didn't feel right and it didn't match with what I saw in the world. I saw purpose and design behind everything I saw. First with technology like computers, cars, and bridges. Then I saw it with society in things like families. Finally I saw it with nature in things like seasons, the food chain, and the movement of planets and stars. Sure there is disorder, chaos, death, and suffering in the world. But beneath the surface there is large scale order and design.
So I realized, if the world was created with a purpose and design, then perhaps so do I. And if I was created with a purpose and design, then I have a creator: God.