- Except that I never could get Joshua to learn the most important lesson.
- What's that?
- Futility. That there's a time when you should just give up.

— (John Wood)

12 seconds sound clip from the WarGames (1983) movie soundboard.

You can hear this line at 01:22:36 in the Blu-ray version of the movie.

Quote context

[...]

- Nature knows when to give up.

- I'm not giving up.

- If Joshua tricks them into launching an attack, it'll be your fault.

- My fault?

- The whole point was to find a way to practice nuclear war without destroying ourselves. To get the computers to learn from mistakes we couldn't afford to make.

- Except that I never could get Joshua to learn the most important lesson.

- What's that?

- Futility. That there's a time when you should just give up.

- What kind of lesson is that?

- Did you ever play tic-tac-toe?

- Yeah. Of course.

- But you don't anymore.

- No. Why?

- Because it's a boring game. It's always a tie.

- Exactly. There's no way to win. The game itself is pointless.

- But back at the war room, they believe you can win a nuclear war... that there can be acceptable losses.

[...]