When Should You Back Down?

The trailer for Never Back Down reveals a movie that is ready to kick the legs out from under the recent danceolution trend, flip it on its back, and pin it to the ground until it admits defeat at the hands of the Fightolution.
But the movie is not merely a run-of-the-mill "I'm dancing to change my life" movie with "ultimate fighting" in place of "dancing." It also serves as an instructional primer for backing down. By watching the protagonist's stubborn resistance to backing down, we as an audience can better gauge precisely how and when we should back down should the occasion arise. Just as those who don't know history are doomed to repeat it, those who haven't seen the trailer for Never Back Down are doomed to never backing down—and let's face it, if this movie is any indication: you should probably back down.
So, according to the lessons learned in this trailer, when should you back down?
—When the lights go down and the action begins