I need certain levels of each of them to continue in a reasonably sane level. Physical energy is the most obvious. I need it to move, be active, all of that. And to keep from being sick. This is earth-energy.
Mental energy is air-energy.
The energy of thought. I find this the hardest energy to replenish, as air is not really my element. Also I play solitaire a lot. Water energy is emotional. Without it I get touchy.