on (your) best behavior

not causing any difficulties.

The two candidates were on their best behavior, giving serious answers to questions from a group of citizens.

Usage notes: usually used to refer to children, but also often used to describe the actions of adults in uncomfortable situations

• have done more than has had hot dinners
• have done more than someone has had hot dinners
• have [done/seen/had etc.] more something than has had hot dinners
• have [done/seen/had etc.] more something than someone has had hot dinners
• have [done/seen/had etc.] more than has had hot dinners
• have [done/seen/had etc.] more than someone has had hot dinners
• have down on like a ton of bricks
• have down on you like a ton of bricks
• have down pat
• have down to a fine art
• have down to a science
• have ducks in a row
• have ear
• have ear to the ground
• have egg on face
• have egg on your face
• have end away
• have eye on
• have eye on someone
• have eye on something
• have eyes in the back of head
• have eyes in the back of your head
• have eyes like a hawk
• have feet on the ground
• have finger on the button