From Longman Dictionary of Contemporary Englishdig your own gravedig your own gravePROBLEMto do something that will cause serious problems for you in the future → dig
Examples from the Corpus
dig your own grave• By continuing to make racist comments before the committee, he really dug his own grave.• I felt the sinking whir of the back wheel as it dug its own grave.• If he went against this young man sitting opposite him, he would in effect dig his own grave.• I thought that before they shot you, they made you dig your own grave first. 