This Roman centurion, an occupying soldier of rank, was given the faith to recognize Jesus for who He is. For I also am a man subject to authority, having under me soldiers... He recognizes the divine authority of Christ, relating it to his own experience of being an authority figure: If he told someone to do something, they did it. Period. Immediately. No arguments. And he believes that Christ has that same manner of authority on a much larger scale, and is able to command obedience even over intangibles like illness.
I am not worthy that thou shouldst come under my roof ... but say the word, and my servant shall be healed. Others throughout the Gospels profess their belief that Christ can heal them if He wishes, as the centurion does here. But more than that, he also clearly understands that, despite outward appearances, Christ so utterly "outranks" him that he is not even worthy to stand in His presence.
We echo these words of the centurion at each Mass: "Lord, I am not worthy that you should enter under my roof, but only say the word, and my soul shall be healed." Domine, non sum dignus ut intres sub tectum meum, sed tantum dic verbo, et sanabitur anima mea. And like Christ healed the centurion's servant despite his acknowledged unworthiness, so too does He come to us in Communion despite our unworthiness.
The concept of "unworthiness" resonates strongly with me, the being made aware of my sinfulness, of how my choices, actions, and words separate me from God. It's so easy to not think about it, to allow cooking and housework and messy diapers and whatever I last read or watched and the Thanksgiving and Advent to-do lists and the kid-created catastrophe of the moment and everything else all day long to quietly just kind of push the concept of "sin" to the back of my mind. And let me tell you, I'm definitely nowhere near holy enough that I always make the right choice that draws me closer to God, especially when I'm not even thinking about the possibility of any and every thing I do bringing me closer to or farther away from Him.
If I'm conscious of my unworthiness to receive Christ, it gives me the push to ask His mercy, to get to confession more frequently, to try to pray more throughout the days and ask for the help to do better. If I'm not made aware of it, none of those things happen. I need those reminders, and I so appreciate them!