Maybe you don't think you can do it.
4 seconds sound clip from the American Graffiti movie soundboard.
You can hear this line at 00:41:30 in the Blu-ray version of the movie.
Quote context
[...]
- Hey, did you know that my ex is going to become a presidential aide?
- Yeah, and it's a secret, so don't tell anybody.
- His greatest ambition is to shake hands with President Kennedy.
- How do you suppose you're gonna do that, wishy-washy, at JC?
- Well, maybe I've grown up. Maybe I changed my mind.
- Maybe you don't think you can do it.
- Maybe I ought to. But I won't.
- Maybe you ought to come into the aft chamber. Where we can discuss this in private.
[...]