I was just talking to my girlfriend about this. I was brought up religious as a child. Going to college was my first experience around a diverse set of religious beliefs, including many non-believers. It only took a few months for me to lose my faith, which came as a shock to me, because I had felt so sure about my world view only a short time before. So I lost my confidence in feelings of confidence alongside my faith. I replaced them both with a very deliberate set of beliefs in things like science and logic.