“When a student comes and asks, "Should I become a mathematician?" the answer should be no. If you have to ask, you shouldn't even ask.”
“It’s not in asking you should fear.Fear comes when you don’t ask.”
“This is a question too difficult for a mathematician. It should be asked of a philosopher"(when asked about completing his income tax form)”
“you should not run for president because tactically you can win. The questions you have to ask are why you're running for president and what will you do when you are president. You shouldn't run until you know the answers to those questions.”
“You asked me to go out with you. I know you probably changed your mind. But you should know, the answer was yes. It's always been yes when it comes to you.”
“You shouldn't ask questions when you know at heart you'd prefer not to hear the answers.”