You don't become great by trying to be great. You become great by wanting to do something, and then doing it so hard that you become great in the process.
— Randall Munroe in today's xkcd, Marie Curie.
I liked this half-hour talk by Ransom Stephens on the life of Emmy Noether (with a nontechnical explanation of Noether's theorem).
It looks like, this month, I get to be the one to start the quotes thread.