What happens when an inspiring quote turns out to be a lie?

I was in church once, more than 10 years ago and the priest said this during his homily. “There are two important days in a person’s life: the day you were born and the day you realize why.”

I know it was that long ago because I came home and wrote what he said down with the date. At the time I thought that was a pretty wise saying. It really cut through the clutter. He was a likable enough guy as far as priests go, so I believed that he had come up with the sentiment on his own.