Seemed kind of obvious to me. Most people who display confidence going into difficult situations do so because they have reason to think they have a good chance for a favorable outcome. Either because of their strength, skill, intelligence, faith, experience, analysis, money, or whatever. And when they are successful they typically attribute their success to those factors. But they don't usually go in thinking they are 100% guaranteed to be successful.
If someone goes into a difficult situation believing they are invulnerable, it is not due to their faith (or boxing skills, or whatever), it is due to their detachment from reality.
Having faith is not a detachment from reality, unless of course you can prove there is no god.