really?; no kidding!; is that so? (sometimes used sarcastically in response to the obvious)

(idiomatic, imperative) Don't wait. Said cynically to suggest that what has just been mentioned is unlikely to happen soon or at all.

used after a statement to indicate an emphatic or ironic negative

(idiomatic, US, informal) Barring unforeseen circumstances.

(idiomatic, ironic) Don't overexert yourself (in doing something that does not require much effort).

(idiomatic, informal) Do not broach that topic.

One should not depend upon a favorable (and typically overoptimistic) outcome to one's plans until it is certain to occur.

A phrase used in response to a question or command in which the target person does not know the answer to or how to respond.

You cannot accurately judge a person solely by appearances.

Indicates that the speaker is not understanding the current subject or situation.