From the food we eat would most likely be your answer,but that is only partially correct. We get most of our energy from sleep. People can go weeks and months fasting or eating very little food and have energy and can function well. We can only last a few days without sleep and our body will shut down. Our bodies recover and recharge during sleep drawning energy from all around us.
Our power plant is really our brain, give it some rest and you regain energy.
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