Awareness of fallibility is an important driver of reliability.

I met my surgeon on a gurney just before a shoulder operation, and joked with him that we had considered writing "not this one" on the good shoulder. He smiled, and then handed my then-wife a pen, saying "Write that. Things like that happen all the time." And I felt that much more confident in him, because I think people who know they can do something stupid are so much less likely to actually do them.