(idiomatic) The survival of the fittest, strongest, or most cunning

(uncommon) Alternative form of when in Rome, do as the Romans do

(idiomatic, US) To perform actions consistent with one's claims.

(idiomatic, US) To attempt to stay cheerful in a dire situation; to proceed with a task, ignoring an upcoming hazard, hoping for a good outcome.

(colloquial) To make a show of bravery despite one's fears; to put on a brave face. / (idiomatic, US) To speak of something despite having little knowledge of it.

(idiomatic) To do things in one's own way regardless of societal norms and conventional expectations.

(idiomatic) To lose one's concentration on what is most important.

(idiomatic) To maintain one's concentration fixed on one important theme.

(idiomatic) To work especially hard, usually for an extended period.

(idiomatic) An attestation to the truthfulness and frankness of an associated statement.