The same thing that happened to me when I didn’t previously believe in God. Nothing (except I will probably be more cynical, miserable, and depressed about life because it makes it kind of pointless if there isn’t a God in my opinion)! God gives us free choice and free will on this earth. Believing or not believing in God doesn’t really change our life on earth much. Good and bad things will happen to good and bad people alike. It is more about what happens after we die, and of course, that depends on what we accept and how we live our lives on earth.
I believe in God, I feel much better. But belief in God doesn’t guranatee a rosy life. In fact, Jesus himself said “in this world, you will have trouble.”