God knows she hadn't always been on her best behavior with him.

Come to think of it, she'd never been on her best behavior with him.

Or people may actually be on their best behavior for a while.

That would leave the rest of us on our best behavior, which is pretty much where we already are.

All evidence points that they were on their best behavior.

Well, the only thing she could do was be on her best behavior in the morning.

Like she was trying to be on her best behavior.

They are also to be in their best behavior while on the island.

I expect you to be very much on your best behavior.

We're all on our best behavior now, with war coming.