From A Short History of Financial Euphoria by John Kenneth Galbraith :

The only remedy is an enhanced skepticism that would resolutely associate too evident optimism with probable foolishness and that would not associate intelligence with the acquisition or administration of large sums of money.

A further rule is that when a mood of excitement pervades a market or surrounds an investment prospect, when this is a claim of unique opportunity based on special foresight, all sensible people should circle the wagons; it is time for caution. Perhaps, indeed, there is opportunity, but a rich history provides proof that as or more often, there is only delusion or self-delusion.

So, comes down to being fearful when others are greedy and greedy when others are fearful. Buffett was right all along with his one liner as was Templeton.