My dad gave me a card with this verse on it when I turned 18, having just graduated from high school. Have never forget it!
My Grandpa did the same thing. I didn't pay much attention to it at the time, but as I grew older and more acquainted with those words they struck me, and still do.
We had to recite this after a night of sorority hazing. I was 16. It's been my favorite poem since.