From there, Father talked about how most people want to do good and have good intentions, but that our good intentions can backfire. As an example, he spoke of today's Gospel reading (Mark 1:40-45), where a leper was healed and then told not to speak about it. Here is the full reading:
A leper came to Jesus and kneeling down begged him and said, “If you wish, you can make me clean.” Moved with pity, he stretched out his hand, touched him, and said to him, “I do will it. Be made clean.” The leprosy left him immediately, and he was made clean. Then, warning him sternly, he dismissed him at once. He said to him, “See that you tell no one anything, but go, show yourself to the priest and offer for your cleansing what Moses prescribed; that will be proof for them.” The man went away and began to publicize the whole matter. He spread the report abroad so that it was impossible for Jesus to enter a town openly. He remained outside in deserted places, and people kept coming to him from everywhere.
The leper wasn't trying to cause trouble. I'm sure his intentions were great, but his actions meant that Jesus couldn't move openly and perhaps couldn't heal as many as He wanted. Father then brought up how often we think we know better than what God is telling us. It isn't that we're trying to do wrong - our intentions are usually good. Even so, we aren't trusting God, but ourselves when we do that. While Father was tying this in specifically with all the statistics about how many Catholics use contraception despite Church teaching (which is truly lamentable), it can be applied to all aspects. It is truly humbling to submit and not trust my own understanding. I'm not talking about abandoning all intellect, for that would be ignoring our God-given reason, but recognising that God has give us the Church and we are to submit to God instead of trusting ourselves.
I hope I've not butchered the homily too much. It was very wonderful.