Maybe you know what you're doing.
3 seconds sound clip from the The Big Knife (1955) movie soundboard.
You can hear this line at 01:25:41 in the Blu-ray version of the movie.
Quote context
[...]
- Charlie gets fanciful ideas about his friend.
- Please, take the library phone and get Nat here right away.
- Maybe you know what you're doing.
- I know you'll wait. You'll wait and wait and wait.
- You mishandle your friends, kitty.
- You're not my friend. That pathetic little girl is my friend.
- Lily? Uncle Hoff, if you please.
[...]