Let’s be honest: for the most part, we gravitate toward people who hold a lot of the same beliefs that we do. It’s human nature. But for anyone in a leadership position, this basic human urge can also be your kryptonite. If you surround yourself with too many like-minded colleagues, that is, you can create a culture of group think. That’s not good. Just take a look back at U.S. history. Lyndon Johnson’s escalation of military action in Vietnam, John F. Kennedy’s invasion of Cuba — many historians have argued that these mistakes were fueled by too many team members refusing to voice their opposition. So every leader should take this advice to heart: never shy away from opposition; welcome it — better yet, encourage it, then encourage it some more.