To remain calm; to avoid becoming angry or annoyed.
get one's shirt out
To become angry or annoyed; to lose one's temper.
keep one's knickers on
To stay calm; to not get flustered or angry.
lose one's temper
To become angry or annoyed.
button one's lip
To remain silent, especially in order to keep a secret or to avoid say…
keep one's cool
To remain composed, calm, and even-tempered, especially in a provocati…
keep one's head
To remain calm, reasonable, level-headed, especially in a situation li…