A dictionary of Confusable Phrases: More Than 10,000 Idioms and Collocations

Note: 
Neither expression correlates in meaning with the phrase
cup of tea, a
—(coll.) an individual of the kind mentioned (es-
pecially an older woman): Miss Prentice seems to be a very un-
pleasant cup of tea.
dig a hole for oneself • dig one’s own grave
dig a hole for oneself —(also: dig oneself into a hole) get oneself
into an awkward or restrictive situation: Melton has dug a
hole for himself that will take the remainder of his term to
come out of. He has made so many promises in his few months
in office…
dig one’s own grave —be the cause of one’s own failure or
downfall: When a plot was disclosed he did not use the occa-
sion to make a comprehensive purge. However humane this
behavior may seem, politically it was digging his own grave.
dig one’s heels in • dig oneself in
dig one’s heels in —act firmly; refuse to yield: It is not an in-
dication of my lack of ability, but rather a sign that it is time
for me to dig my heels in and exert more effort.
dig oneself in —(also: dig in) 
1
. (of soldiers) dig a protective
place for oneself: We were ordered to dig ourselves in and I
can assure you that it did not take us long to dig our trench.
2. establish oneself securely; get oneself settled (in a new job,
etc.): I am relatively new to the photography world although
I’ve dug myself in and tried to improve as much as I can.
dime a dozen, a • ten to the dozen
dime a dozen, a —said of people or things that are very com-
mon and easy to get: Fad diets are a dime a dozen. It seems
like every time we turn around there is a new diet.
ten to the dozen —(also: nineteen to the dozen) talk very fast
and without stopping: Everybody is talking ten to the dozen
about the fantastic film material they’ve shot.