foul your own nest
foul your own nestLITERARY
If someone fouls their own nest, they do something which harms themselves and damages their chances of success. Man has invented a hundred ways of fouling his own nest — the grime, the pollution, the heat, the poisons in the air, the metals in the water.
foul your own nestdo something damaging or harmful to yourself or your own interests.
The proverb it's an ill bird that fouls its own nest , used of a person who criticizes or abuses their own country or family, has been found in English since the early 15th century.