1. Cool Your Jets -

: Specifically used when someone's anger is "boiling over". Keep your shirt on : An older idiom for staying calm. Pop Culture Connections

The phrase emerged in the during the mid-20th century, a period deeply influenced by rapid developments in aviation and the "Space Age". 1. Cool Your Jets

or Take a chill pill : Modern, very informal ways to say the same thing. : Specifically used when someone's anger is "boiling over"

: A classic alternative for advising patience. Space Cadet series

: One of its earliest recorded uses is in the 1952 novel Stand by for Mars! from the Tom Corbett, Space Cadet series, where a character is told, "Cool your jets, space creep!".