The quote is: "Investors should remember that excitement and expenses are their enemies. And if they insist on trying to time their participation in equities, they should try to be fearful when others are greedy and greedy when others are fearful."
Yes that's the quote I was thinking of, I think he also said it during a talk with Bill Gates on CNBC during 'Keeping America Great' special: http://classic.cnbc.com/id/33604479