Galbraith on Speculative Episodes

In John Kenneth Galbraiths's book A Short History of Financial euphoria he writes:

A further rule is that when a mood of excitement pervades a market or a surrounds an investment prospect, when there is a claim of unique opportunity based on special foresight, all sensible people should circle the wagons; it is the time for caution.

Caution indeed. Galbraith's book has much wisdom and understanding.