Alternative form of I know you are but what am I

(Chinglish, Singlish) I don't know, how should I know

(idiomatic) It is not possible to repeat past experiences, as time changes all things.

Used to suggest dating someone.

Do not seek advice from a biased party.

Alternative form of you can't put the toothpaste back in the tube

Once something is said or done, it cannot be unsaid or undone.

Alternative form of you only go around once

Synonym of you don't dip your pen in company ink

(informal) Used as a rhetorical question to confirm agreement, knowing or understanding at the end of a statement.