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Colonial Hanoi in 1902 was overrun with rats, so the French administration offered a bounty for every rat eliminated: you only had to hand in the tail. At first it worked. Then tailless, very much alive rats began appearing around the city — people were releasing them so they could keep breeding — and some went as far as setting up rat farms. The plague ended up worse than before.
The plan was not stupid: it was first-order. It solved the immediate effect ('fewer rats') without asking what people would do once the incentive existed.
The tool is uncomfortably simple: before deciding, ask 'and then what?' at least twice. First answer: what you want to happen. Second: what everyone else will do once it happens. That is where crash diets die, along with promotions that attract exactly the customer you did not want, and shortcuts that pay you this week and charge you the next.
Second-order thinking is not pessimism: it is playing out the whole game in your head before moving the first piece.