I think there’s a fine balance between your certainties and over confidence and questioning yourself and doubting yourself. As a rider you have to find a balance. Personally, I am constantly questioning myself, watching videos and trying to improve. Every rider can always improve.
In college, there was a strong emphasis on critical analysis of both others and yourself. You would be filmed and expected to analysis the video. You learned to remove the personal from the situation. We'd also ride around and be expected to tell the lecturer what the good and bad bits are, who would then confirm it or tell you where you're going wrong, or show you something you need to focus on. Basically, it taught you to ride independently.
In saying that, there's always an element of self in whatever you do. You can never really be completely unbiased about yourself, which is why instructors and lessons are necessary, regardless of your level.