know when to fold 'em

An allusion to a poker player knowing when to cut their losses rather than continue in an unfavorable situation.

know when to fold 'em (third-person singular simple present knows when to fold 'em, present participle knowing when to fold 'em, simple past knew when to fold 'em, past participle known when to fold 'em)

1. (slang, informal) To exercise sound judgment in a situation that is precarious and uncertain.