Dig (one's) own grave phrase
If someone "digs his/her own grave", he/she does something that is considered to be self-destructive or self-sabotaging. His/her action will lead to a negative outcome that is easily predictable.
OMG! Bob is digging his own grave when shouting insults to the police.
Linda always destroys her relationships while they are going well. She digs her own grave, indeed.
A: "What's the matter with you?" B: "I dug my own grave. Last night, I was fuckingly drunk, and I said bad words to my colleagues."
The verb "dig" should be conjugated according to its tense.
The phrase dates from the first half 1900s.
A humorous way of saying that what one has said is just what they acknowledge and may not be entirely accurate
Mike: Have you returned from your vacation on the beach? Your skin seems to get tanned.
Jenny: My skin is always dark. That's my story and I'm sticking to it!