Straighten up and fly right
Straighten up and fly right (English) — Most commonly used as an imperative with parents to children. "You better straighten up and fly right." It means that someone's conduct is below the level it should be or that they are involved in conduct that is undisciplined, unacceptable. It implies bad consequences.
Nat King Cole and Irving Mills wrote a song about it in 1943. It's about a buzzard and a monkey.