During college, and perhaps immediately after, I would have traveled more, gotten outside of my comfort zone, interned or worked elsewhere and tried to see more of the U.S. and world instead of a little boxed cocoon that stifles the imagination, understanding and knowledge.
I've encouraged our two college-age kids to do this, within financial and safety considerations. I have friends whose same-age children and other friends who have traveled to Europe, Asia and parts of Central America for work or vacation. It was rewarding for them.
Also, would have been far more patient and not traveled as much for work. And begun running 25 years ago instead of five years ago.