An Open Mind
G. K. Chesterton once said that "The object of opening the mind, as of opening the mouth, is to shut it again on something solid."
Close mindedness is often pride masked as confidence. I've taken this frame of mind often in my life. I've refused to listen objectively because I assumed there was no way the other person was right.
Humility, though, recognizes the potential for failure, for error. A Christian who believes he is always right is a contradiction. We are Christians because we believe Jesus had to die for our errors.
The danger here is to then assume you are always wrong — that because we are sinful we are always in error. This is not true. It's impossible to live with the assumption that you are always wrong.
The right frame of mind is the balance between the two. While we can be wrong, we must seek to find truth. This is where a true open mind becomes useful.
An open mind allows you to filter through the possibilities, to listen with interest, and then come to a conclusion you think is true. The point of an open mind is not to remain open, but to find what is true.