"Think For Yourself, Schmuck!", one of the central dogma/catma of Discordianism.

Similar and related phrases in this context are "Question Authority, Think for Yourself", "Black Sheep are still Sheep", "The Map is not the Territory", "Don't Eat the Menu!", "Do What Thou Wilt Shalt Be The Whole Of The Law--But Remember Nobody Likes an Asshole!", "A Conclusion is Simply where you Stopped Thinking" and of course being forbidden to believe anything that is written.

When you eat dirt for the first time and leave your family to build a shack in the woods

The Fuck You Say? Used when someone says somehting that generally disgust you, confuses you, or just makes you mad.

Basiccally standing for "Think for yourself", can be used in a criticizing or encouraging manner.