The following is a very interesting exchange between Richard Bandler and someone who is very sure about something.
B: Are you sure?
P: Yes.
B: Are you sure you're sure?
P: Yes.
B: Are you sure enough to be UNSURE?
P: Yes.
B: OK, Let's talk.
Before reading further, I strongly recommend that you think of something that you are very certain about, and find someone else to ask you this set of questions about your certainty, so that you have a concrete personal experience of their impact. At the very least, close your eyes and imagine that someone else asks you these questions, and take the time to carefully notice your response to each one, so that you can experience their effect on you.
And for those of you who teach modeling, or do modeling, this is an excellent small opportunity to do some of it. Although Bandlers exchange is brief, and concise, it is quite interesting to explore its structure.