omae/お前=impolite form of YOU. Do not use this word unless REALLY angry. Instead use the person's name or, if you must, "anata".
jibun/自分=oneself
BTW, this could be used to refer to your own person ("me") or someone else. ("yourself" or "you")
jibunde/自分で=by yourself.
no/の='s
boketsu/墓穴=grave
wo/を=article indicating the receiver or object of the verb
horu/掘る=to dig
hotta/掘った=dug (past tense of horu/掘る)
na/な=just a stressor
Ironically, despite the similarity to the English expression, in Japanese this is actually not as strong as to dig one's own grave. I'd say it's more like "to shoot yourself in the foot."
STUDY!
dig grave guy Japanese Lessons own tough Your idiom proverb