I've had the chance recently to see a little of Luke Cage (four episodes at time of writing this), and it's good. I'll hopefully talk about it a bit more when I finish, but I had a thought, watching it.
Luke has unbreakable skin, or invulnerability, or whatever you want to call it. What I wondered, watching people try futilely to shoot him, does he still flinch? Is he wondering if whatever the experiment did to give him those powers is about to wear off? That maybe the next bullet won't deflect harmlessly?
This isn't something exclusive to Luke Cage. You could say the same of Superman - and not just with the invulnerability, but also flying. If I had flying powers I'd be terrified to go too high in case they vanished suddenly - or anyone similar. I think it was a combination of Luke's initial reluctance to use his abilities publicly, and then, when he makes the decision to hit Copperhead's vault, the confidence/swagger he exhibits, that made the question come to mind.
Luke hadn't seemed entirely comfortable with the results of what had been done to him, but I don't know that you could fake that confidence. He's not putting his hands and arms up to shield himself, or turning his head away. Those would seem to be reasonable, reflexive responses. Hell, Tony Stark puts his arms up to block bullets, and he's wearing a super-awesome suit of power armor he built, meaning he knows exactly how resilient it is. But he still shields himself. Not Luke, though. He walks ahead steadily while they shoot at him. Until he reaches them, at which point they don't get to shoot at him any longer.
The powers can give someone the confidence to do things they'd never normally attempt, but using them means that person also has to have confidence in those powers. That they're up to the challenges. Again, not something exclusive to Luke Cage, but he (and Mike Colter's performance) were what prompted all this.