It is interesting we feel that way. Our faith is not just about what we cognitively believe. It is also about how our beliefs affect our lives. They affect our emotions and they affect our behavior. If we believe right, we feel confident.
Faith comes by hearing. . .
One answer is that we maintain an attitude that is aware that we could fall. Another is that we thoroughly enjoy God. There are other good answers as well. I listened to a fascinating tape the other day that talked about boundary markers as a means of identifying a group. The idea is that every group has several very visible, though somewhat trivial evidences of who is and who is not in the group.