One in twenty.
The ever present chance of failure. It’s a motto I use to curb the sin of conviction. If you’re a fellow nerd you may recognize it from Dnd, because yes, I did steal it from an RPG. Despite it being a game mechanic that had purely practical reasons for existing, it can be interpreted philosophically. Always remember you might roll a one. I’ve definitely frustrated people by refusing to be “100%” sure of anything and it’s for this very reason.
You can always be wrong. In fact, assuming you continue to live and learn, you’re probably wrong right now. Not about everything but about some things and you can’t know what. Keeping an open mind means accepting that there’s a chance you’re wrong.