Is knowledge dangerous?

Believing you've achieved all of the knowledge you need is dangerous. Pride sometimes leads one to believe they've acquired all of the knowledge they need to complete a task, but they haven't. People believe they've prepared themselves for certain things and they have..... in regard to the things they've studied, but they forget that experience is as important to gaining knowledge as studying a book. Chris believed himself prepared for anything, almost as if he were invincible, but things came up he didn't forsee, and other things went wrong because he wasn't as prepared as he believed himself to be.