In this, my second Lent as a priest, I'm beginning to realize why self-denial is a critical part of the priestly life. You have to practice it in order to counteract the forces that conspire to make you selfish and arrogant.
As a religious who is not or not yet a priest, few people "get" who you are, and you are constantly explaining, often in vain, that you are a lay Catholic religious and not a priest, a Buddhist, or one of those martial artist monks from the movies. In one hectic morning it all changes and you are a Catholic priest and everyone knows--or think they know--what you are, friends and enemies alike.
In a lot of ways this becomes a spiritual hazard to the minority and humility that is sought in the consecrated religious life. As a priest you are often the center of attention. You are given the seat of honor at events. People old enough to be your grandparents address you by title. Since the ministry of priesthood is so diverse, you are bound to good at something at least, and are praised endlessly for it. You attract disciples who treat you with reverence. You become more appealing to the opposite sex because of your power and unavailability.
It's easy to let this "go to your head," and maybe that's what happens to priests who become self-centered and arrogant. Subtle signs illuminate the path to this spiritual death: You look forward to seeing your flatterers and, enjoying their comments, forget that it is those who insult you who are your real spiritual friends. Instead of asking people about their own lives, children, and folks who might be sick or struggling, you notice yourself turning conversations back to yourself as you grow accustomed to being the center of attention.
These sorts of things have to be fought with the utmost ascetic effort in order to prevent them from becoming habits. This is why plain, unglamorous, and elementary forms of self-denial over the course of a day are so important. They train the self not to concentrate on its own wants and whims and open the inner door to concern and focus on others.