We have a Japanese old saying, “俎板の上の鯉－manaita no ueno koi, a carp laid on a chopping block” for describing (1) a critical situation you cannot avoid, and (2) a person who is self-poised at such a critical moment.
This metaphor comes from the legend that carp is still and composed unlike other fish, like eel when laid on a chopping board. I think it corresponds to the spirit of ‘葉隠-Hagakure’, the Bushido’s bible written by Yamamoto Tsunetomo, a senior samurai in Saga-Nabeshima fief in 1716, in which he says the ultimate goal of Bushido is to recognize when, where, how, and for what you should die.
Though I’ve never seen a carp placed on a cutting board, we use this simile for various occasions for facing predicament and requiring rational judgment / action in such a way; “The company is considering a massive layoff, I’m a carp on a chopping block,” “The governor behaved like a carp on a chopping block when he was sued for sex scandals,” "My husband said "I'm a carp on a chopping block," when he was told he was at the terminal stage of cancer by his doctor."
Are there metaphoric expressions similar to “a carp laid on a chopping block” which implies keeping composed at eleventh hour, preferably using a bird, beast, or fish, like a carp?