Luck can be a fundamental part of roleplaying games. Many games use dice as a randomisation tool, to determine the outcomes of actions according to some random probability distribution. Whether you hit an enemy in combat, or manage to avoid a poison needle trap, or cast a spell successfully, comes down to chance. You might have a better or worse chance, depending on your skill level and the difficulty of the task, but in the end the dice control the result.
People like having some randomness in games, as it builds tension and excitement, and it occasionally lets you get away with audacious things that wouldn't work nine times out of ten. That can be fun!
But what the dice giveth, the dice taketh away. With the chance of reward comes the risk of failure. In the long run, failures are going to be inevitable. So you need a method to deal with them that doesn't involve instantly killing characters or destroying their chances to succeed in their longer term goals. Failures should be setbacks or complications, not death sentences. (Unless players are deliberately engaging in super high risk activities, where the possibility of extreme failure is known in advance, or just being plain stupid in the face of certain death.)
Commentary by memnarch (who has not seen the movie)
So..... Rey finished her training already then? This is a heck of a jump from having the Force helping out once. She has to be suggesting these things in the movie though, right? Rey doesn't look that surprised by what the guard is doing, and she's clearly saying something.
Hmmm. Or perhaps the guard is just acting like they're being controlled? A proper set-up for a dangerous prisoner should have at least two guards on duty all the time I feel. I can't see why the First Order would benefit from Rey escaping, but they definitely don't lack the personnel required for a meager two-person guard detail. Especially in the movie, where there probably isn't a trade being talked about, and we can already see that Kylo Ren wanted Rey for something. Another potential spy, this time an unwitting one, perhaps?
And of course, the guard wasn't told not to raise the alarm. I wonder if the GM will end up using that fact against Pete. There would be a good number of opportunities to spring that trap, like just before Rey can transmit a message to the Resistance saying that she's escaping, causing all comms to lock down.
Transcript
Rey: You will remove these restraints. And leave this cell, with the door open.
GM: The guard walks over to glare at you.
Trooper Guard: Why is it that people who can’t take advice always insist on giving it?
Rey: I roll 13.
Trooper Guard: ... I’m all ears.
Rey: You will remove these restraints. And leave this cell, with the door open.
Trooper Guard: Allow me.
GM: The guard releases your bonds and walks out.
Rey: And you will drop your weapon! 18! If it’s not too much trouble.
Trooper Guard: Do I look like I give a damn?
[SFX]: clunk {he drops his blast rifle}
Rey: Too easy.
GM: Half of everything is luck.
Rey: And the other half?
GM: Fast talking the GM.