Every failure is a valuable experience.

The most important part of teaching is to teach what it is to know.

The man who speaks to you of sacrifice, speaks of slaves and masters. And intends to be the master.

Mathematics is not a deductive science—that's a cliché. When you try to prove a theorem, you don't just list the hypotheses and then start to reason. What you do is trial and error, experimentation, guesswork.