This is part of my Sara of Cybertron story where it's mentioned that a safe word had been used a few times in training

Sara was doing hand to hand combat training as part of the reintegration for her to be recognized as a military officer again. It was hard work but she didn't care, she was determined to succeed and complete her training as fast as possible. Anything less just wasn't acceptable.

Suddenly her eyes glazed over and no longer focused. At first no one realized what had happened but when she beat her opponent and acted like she was still fighting, the instructors realized what had happened. As soon as the the first instructor noticed it, he quickly alerted the rest

"She's having a flash back!"

Another instructor quickly started giving orders and also at the same time tried to calm Sara down

"Everyone keep back, Lt. you're safe, you're in hand to hand combat training, not in a fight for your life. It's not the war Lt. you aren't in any danger"

Unfortunately it was quickly realized that the words simply weren't working like they were intended to so the chief instructor made the call

"Has the doc been called?"

An instructor who was on standby for medical issues spoke up

"He's here now"

"Good, doc if the safe word doesn't work, you're going to have to sedate the Lt. so that she's not a danger to herself or us"

"Right, I'm ready chief"

"Lightfoot!"

That word stopped Sara in her tracks and they visibly noticed her coming back to them and then she was on her knees shaking horribly. Finally though, she spoke

"Did I go away?"

The chief instructor spoke up, letting the rest of the instructors know that he was now in charge of the conversation with the Lt.

"Yes, but thanks to the safe word you came back"

"Thanks sir, I needed to hear that"

"Which battle were you fighting this time?"

"I...I was actually in the fight ring this time"

"You mean when you were taken prisoner for three years?"

"Exactly sir"

"I understand, think you can continue or do you need to go back to the bunker and get some rest"

"I should be able to continue sir and if I feel it necessary, I'll head to medical"

"Very well then"

With those words Sara continued the training that day and even though it was a long struggle, eventually became a soldier again