'twas a joke.
CoachPro got it, you didn't. That's fine.
I was just illustrating my physics point: Once you've used up all of your energy, it's gone. It doesn't matter how much you started with, once it's exhausted, it's gone until you go get more.
And that's why Aliens are always attacking Earth in those sci-fi films. They use up all their energy like there's no tomorrow, don't bother to conserve, and end up running out... so they come to Earth to get more.
Ditto for fighters who don't manage their energy in the early going of a fight. They blow through everything they have and, since there's no Taco bar in the cage between fights, that's it. It's gone. They don't have any access to more energy. Having 'good cardio' doesn't change this.
You might have twice the cardio and twice the energy available to you as the guy you're fighting... but if you decide to use all of that energy in the first round, you're screwed.