A friend in the recovery community explained to me that one of the things which characterizes many people in AA programs is that they have "a large ego which is very frail." I'm not in AA but I can understand what he is saying. It is a strange irony when people who think they are very important are so easily upset whenever someone brings turbulence into their ideal world. I understand this because I can be this way more often than I want to.
As we talked about it further the image that came to my mind was that of a giant pimple. This is intentionally a very gross metaphor. Think of a large pimple. It is sensitive and filled with puss, so when it is popped the nasty insides are shot all over the place making everyone feel horrible. Similarly, when someone has a large, yet frail ego, very little thing that rattles the serenity of their world can cause the ego to pop, and when it does nastiness comes spewing out all over the place in the form of anger, harshness, addiction, self-pity, and lashing out.
Jesus doesn't want his followers walking around like ginormous red pimples. This is why he spoke through the Apostle Paul in Romans 12:3,
For by the grace given to me I say to everyone among you not to think of himself more highly than he ought to think, but to think with sober judgment, each according to the measure of faith that God has assigned. (ESV)The way of the Christian is to live with a "very small ego that is impenetrable" because it is purchased, rooted, and sustained by the death and resurrection of Jesus Christ and his life giving grace.