Manufactured goods are then sent out into the world. A human being is an open system, too. This is true of energy usage in all life processes, from breathing to dying. When the flow is balanced and smooth, you feel good. When there is interference at any point the in input, the output, or inbetween you can feel empty, pressured, or blocked.
Illness is often the result.
The process may be compared to the movement of water through a pipe. The source of the water, the reservoir, constitutes the input. The size and condition of the pipe will determine the flow through. Whatever the problem, it is obvious that the amount and the quality of water at the faucet, the output, will be seriously affected. Overuse, due to extreme need, such as putting out a huge fire, may quickly deplete the input source.