Modesty and arrogance aren't true opposites. It's quite common, especially with more junior developers, to overestimate one's own skills and underestimate other

Modesty and arrogance aren't true opposites. It's quite common, especially with more junior developers, to overestimate one's own skills and underestimate other's. Not having some sense of modesty and trying to step on others to get to the top will win you more enemies than friends and someone who is unpopular with their colleagues doesn't usually do a very good job at leading.