rod for one's back

noun

1. The means of one's own punishment or downfall.

   “"Silcote, you are making a rod for your back in your treatment of that child. She'll live to break your heart for you."”

   “Nobody is more wary of Tony Blair's record ratings and the illusion of the Prime Minister's omnipotence than Tony Blair himself. "He thinks his approval ratings are a rod for his back," says one adviser.”