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

Note: 
The expression does not correlate in meaning with the
phrase don’t give up the ship— used to tell a person not to sur-
render and keep on trying or working on smth. till he gets it right:
Keep up the good work and don’t give up the ship, just yet.
There is light at the end of the tunnel!
give something up as a bad job —stop doing smth. because
one does not feel it is worth continuing; acknowledge that
one has no hope of success: I tried to make him see things as
I did, but when this effort failed, I gave it up as a bad job.
don’t knock yourself out • knock yourself out
don’t knock yourself out—(coll.) 
1
. don’t overexert yourself in
an effort to accomplish smth.: Don’t knock yourself out trying
to track down your child’s allergies unless they truly are per-
sistent. 2. (ironic) don’t overexert yourself in doing smth. that
does not require much effort: “Well, don’t knock yourself out
to say something, Sarah,” he said. His tone was teasing, but
his eyes were not.
knock yourself out—(sl.) go ahead; do as you please (usually
in answer to a proposal a person is not happy with): If you want
to make hotel and airline and car reservations and take care
of everything, well, then, knock yourself out.
don’t mention it • don’t talk to me about it
don’t mention it—is used to indicate that thanks or apology
are unnecessary: I wanted to apologize for not having known
him in the garden. “Don’t mention it,” he enjoined me ea-
gerly.
Note: 
a) The expression does not correlate in meaning with
the phrase don’t mention the war—(UK) don’t speak about
things that could cause an argument or tension: In today’s world
of “don’t mention the war” or say anything to upset the Eu-
ropean Union, I really did believe these great little reads had
long disappeared.
b) The expression does not correlate in meaning with the phrase
never tell me
—(also: don’t tell me) used to emphatically express
incredulity or disappointment: “Rosalie, never tell me you’ve
been talking about Alexi this whole time!” “Why, yes,” said
Rosalie in dismay.
don’t talk to me about it—is used as an exclamation against
discussing smth.: If you want to know more, read a book, or
talk to Sharon or Allison. Just don’t talk to me about it any-
more.
See also: don’t tell me / say no more.