Help with a German phrase.... incomplete

Long story short, a girl at a bar said a phrase to a friend of mine and being english speakers we only remember part of it and cannot find out what she was saying.

The part we remember was "..... du bist ein grosser junge..." but there was something else. She said it was a common saying in German and that he could figure it out..... help, its really got us wracking our brains.

Tu es un grand jeuness.

"Du bist ein grosser Junge" literally means "you're a big boy now" and is sometimes used to say "you're old enough to take care of your own matters now".