Jesus keeps talking about His coming death and resurrection, and the disciples don't dare talk back about it anymore. Instead, they argue about which of them is greatest! Jesus tells them that the great will serve, receive children, welcome help from allies, keep from causing others to sin, and be severe with their own sin. A good disciple has the unquenchable fires of hell on his mind.
Sins this may reveal
We like to change the subject and set our attention on pleasant things like how great we are. We will go to great lengths to avoid focusing on Christ's cross and ours, and on the hellfire that is the end destination of the path of our selfish ways.