Doc: "Marty, why are you wearing that gun? You're not considering going up against Tannen tomorrow?"
Marty: "Doc, tomorrow I'm going with back to the future with you, but if Buford Tannen comes lookin' for trouble, I'm gonna be ready for him. You heard what that son of a bitch called me lats night."
Doc: "Marty, you can't go losing your judgement every time someone calls you a name. That's exactly what causes you to get into that accident in the future."
Marty: "What? What about my future?"
Doc: "I can't tell you. It might make things worse."
Marty: "Wait a minute, Doc. What is wrong with my future?"
Doc: "Marty, we all have to make decisions that affect the course of our lives. You've gotta do what you've gotta do, and I've gotta do what I've gotta do."