It's funny because it's true

"The lesson of Vietnam is that once you make the initial mistake, little you do afterward is right."
linked from Atrios

This has been put even better in Higgin's crime novel "Digger's Game", where the hitman says of his victim (from memory)

"He made two mistakes. The first mistake was knocking over the craps game, and the second mistake was making the first mistake, the way it always is."

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