You know when you're watching a movie/TV series or reading a book and they use a trope that breaks the story for you? Let me comment some common tropes that just trigger my facepalm reflex whenever they are used.
The 100% brain myth.
You already use 100% of your brain. Just not all the time. The brain is divided in specialized systems that are activated when needed. If you had your brain set to 100% all the time you'd be on the floor with a sensory overload and full body spasms as your brain activated every muscle in your body at once... Not a nice experience I'm sure.
It's working at 150% efficiency captain!
No. Just no. Nothing in the Universe works even at 100% efficiency. You always lose some energy in the form of heat, sound, radiation, etc. If something worked at 100% efficiency you'd be witnessing true magic. Is it too hard to say you managed to improve energy output to, let's say, 20% above specifications?