dig one's own grave

dig (one's) own grave

To do something that has or will have negative consequences that are easily able to be foreseen. If you don't turn in your project, you're digging your own grave. There's no way you'll get a decent grade without it! I'm afraid I'm digging my own grave by turning down the promotion.
See also: dig, grave, own

dig one's own grave

Seriously harm oneself, cause one's own ruin or downfall. For example, If Sam pursues that course, he'll be digging his own grave. [First half of 1900s]
See also: dig, grave, own