Every teacher likes to think that he or she is "the best." Sure, there's always more to learn. But a certain amount of ego becomes involved the more you teach. After a few years and a few dozen students under your belt, it's only natural to feel that your process of trial and error has left you better than when you started. And, arguably, it has.
The unwitting result of all this is a vein of competitiveness. You become the clan leader of your little tribe of students and no one dare invade! Every alternative idea is not only a threat but a potential blow to that ego.
The thing is, teaching should not be competitive at all. Where did you get your first teaching ideas if not from other teachers? The only way to keep the classroom engaging is by trying new approaches, seeing if it works and then making the approach your own. This is the true trial and error process.