keep (your) shirt on

to stay calm.

The meeting may be pretty unpleasant, so promise me you'll keep your shirt on.

Related vocabulary: keep your cool

• under fire
• under heel
• under lock and key
• under no circumstances
• under nose
• under own steam
• under pain of death
• under shadow
• under someone's heel
• under someone's nose
• under someone's thumb
• under something's shadow
• under something's thumb
• under the banner of
• under the banner of something
• under the circumstances
• under the counter
• under the gun
• under the influence
• under the knife
• under the skin
• under the sun
• under the table
• under-the-table
• under the weather